Medium-frequency requests quantity. High-frequency, mid-frequency and low-frequency inquiries are free. How to check the competition

Keywords that are included in the semantic core of any project have, from which the priority of their promotion or use in their materials may change. One of these characteristics is the frequency of the request.

What is Request Frequency?

The frequency of the request is the number of times that the user entered this request in the search engine string for a certain period of time. One of the most popular and affordable services for checking the frequency search queries is the Yandex service - Yandex.Wordstat (wordstat.yandex.ru). Accordingly, the more frequent requests we use in our materials and articles, the more traffic we will receive. However, not everything is so simple, and first you need to understand the types of frequency of requests and their application.

Types of request rates

In SEO, it is customary to classify queries by their frequency. It is believed that the higher the request frequency, the more traffic it will bring(if you look strictly at the numbers).

Frequency types are as follows:

    High-frequency requests, they are also HF requests.

    Mid-frequency requests, they are also mid-frequency requests.

    Low-frequency requests, they are also low-frequency requests.

This classification is used by SEO specialists in their work. For example, when communicating with colleagues, in order to indicate the traffic potential and the difficulty in promoting a particular group of requests.

Frequency of request as a relative value

Frequency is not an absolute value. It reflects user demand for certain goods or services in a specific niche... It turns out that if you take all queries in the "notebooks" category and sort them by frequency, then the first place will be a one-word query with a frequency of 5,295,645 impressions per month (conditionally). If we are talking about the niche "cat food", then the upper threshold there can be much lower, about 249,968 impressions per month.

It follows from this that we will assign the form to the request based on the upper threshold of frequency in the topic. As a result, we will have 3 groups, for each of which a frequency threshold for phrases that are included in this group will be assigned.

For example, for the "children's trampoline" theme, the boundaries will be as follows:

  • HF - everything above 20,000 impressions per month
  • Midrange - from 3,000 impressions per month
  • LF - up to 3,000 impressions per month

You shouldn't stick too much to boundaries and spend a lot of time classifying queries by type, because this segmentation is rather arbitrary and has no practical value.

High Frequency Interrogations (HF)

High-frequency requests (HF) are requests that have the highest frequency rates among all requests in our chosen niche. As mentioned above, an RF request can be either with a frequency of 5,295,645 impressions, or with a frequency of 27,811 impressions, as you can see from the example below. In some topics, for example, a request less than 5000 is no longer high-frequency.

Almost alwayshigh-frequency queries are token queries, one-word, or the so-called.

Examples of such queries are “computer,” “car,” “apartment,” and other general queries.

Photo 1: An example of a super-high-frequency request for a niche with stable, heated demand.
Photo 2: According to statistics, cars are the second most popular topic for discussion among men.

An example of narrower, but high-frequency queries might be the following phrase (only if our niche is express weight loss courses):


Photo 3: Losing weight, losing excess weight is perhaps the most pressing problem for women. The frequency of the request signals that there is a clear demand for a given topic.

The request is not one-word, but the semantic meaning or intention of the user is clear from it, as opposed to the request “car”, when it is not known whether to show him a site for car repair, car wash or sale.

The advantage of high-frequency requests is potentially high traffic. The difficulty lies in the fact that there is unrealistic competition in high-frequency queries and it takes a lot of time and effort to get to the top for them.

Important! Do not try to promote a young resource exclusively for HF requests, it will be much more profitable to focus on promoting MF and LF requests for the rapid growth of the project.

As practice shows, high-frequency requests make up no more than 5% of semantic core project. There are times when one common (HF) request covers 50% of the frequency of all other phrases from the core. This is a normal situation.

We can understand the relative difficulty of promoting a particular keyword by evaluating its competition index. You can compose the index yourself by analyzing the results, or you can use the Mutagen service, which will calculate the index using your own formula. For example, if we see that, according to Mutagen, the competition of phrase 25, then we will not advance on it soon and it is better to focus on other, less competitive phrases.

Medium Frequency Requests (MF)

Medium Frequency Interrogations (MF) are the group of interrogations following the RF interrogations. For different topics of the midrange, requests can start from both 1,000 and 50,000 impressions per month.

Mid-range queries are usually (but not always!) Less competitive than high-frequency queries. In them it is possible to find queries with a longer "tail" and less competition... In addition, the midrange query in most cases contains more words. Thus, it is easier for us to understand the intent of the user who entered this request and show him an article with a solution to his problem or offer a product.


Photo 4: Such queries make up about 10% of the semantic core of the project.

It is easier to promote midrange queries than high-frequency ones (for the most part) and it can take less time and effort. However, in this case it will also be relevant to look at the competitiveness of requests in order to build the right strategy for promoting documents (pages) on the site.

Low-frequency requests (LF)

Low-frequency queries are queries with a frequency of less than 1000 or 100. It is this type of queries that is most interesting SEO specialists and semantics, because they can make up 80-90% of the entire semantic core.

Why are there more such requests? It's simple. Many people, when they drive a search query into a string, for example, Yandex, know in advance what they need.

Interesting fact! People learn to work with search. According to a study by Yandex, in 2016, people entered 30% more 7-word phrases than they did in 2015. Thus, the "tail" of requests will grow further, and the user will refine his request more and more.

Example. There are 2 people - Petya and Masha, both want to buy a multicooker. Petya is an amateur in this business and does not know what types of multicooker are, so he wants to see everything possible options... Therefore, his request may look like a high-frequency - "multicooker".


Photo 5: As a first step, Petya decides to just see what he has to deal with.

Masha, on the other hand, consulted with her friends and knows which product to take. Therefore, her request may look like this "multicooker polaris pmc 0347ad".


Photo 6: Masha found out everything from her friends for a long time and went straight to compare prices.

Moreover, in this case, there can be several options for writing a request - “multicooker polaris”, “multicooker polaris pmc”, “buy multicooker polaris” and so on. If we assume that each person tries to find the model of a multicooker that interests him, then at least 100 requests will be collected.

In some topics, requests may appear due to a lack of knowledge or names of any things, diseases, products. Differences in knowledge, vocabulary, experience of people who enter queries into the search bar generate a large number of low-frequency queries.

For example, one user types in the query: "How to grow a money tree?" In fact, these requests are about the same, but the second request will be less competitive and less frequent than the first.

Competition for low-frequency requests is usually small and it is not difficult to advance on 95% of them.

In no case should you ignore low-frequency requests. It is not uncommon for a large number of low-frequency requests to make up 80% of a project's traffic due to the quantity, while HF and MF requests the remaining 20%.

Another characteristic feature of LF queries is the “long tail” of the query - that is, a query with a large number of words. For example:


Photo 7: And also + free + without registration + without SMS.

Gathering groups of similar low-frequency queries, led by the 1st marker


Photo 8: Tails "with their own hands" and "at home" - these are twins brothers. Usually, if you see one in the request, then sooner or later you will find the second :).

We will receive a full-fledged group of requests and will be able to write good material that will advance on low-frequency requests and gradually, increasing the confidence of the project and document, will rise to the TOP and on high-frequency requests.

Outcomes

We examined the main types of HF, MF and LF requests. Summarizing the main part, the following recommendations can be highlighted:

    Don't focus on RF requests. If our core consists mainly of high-frequency queries, then there will be difficulties with its implementation and promotion. It is better to supplement it with midrange and bass and then implement it. In this case, it will be much easier to promote the project.

    If we want to advance on RF requests, then it is better to first assess the competition of each of them in order to better understand where the result will be faster.

    Do not ignore low frequency requests. It is they, due to the number and total frequency, that help to cover all the semantics and desires of users and, as a result, get traffic to the site.

    Before the implementation of the SN, it should be analyzed for the amount of HF, MF and LF - this will help determine how complete the core is in front of us. If HF requests are 50%, MF - 30%, and LF - 20%, then there is the potential for expanding the SA due to MF and LF. ...

One of the defining moments in the process of effective website promotion is filling thematic content on its pages with keywords and expressions, or, as they say among professionals - keywords... The final success of promoting the resource to the “tops” of search engines for certain search queries of Internet users will largely depend on how skillful the selection of the latter will be.

Speaking about keywords and expressions, it is worth noting that in the circle of specialists it is customary to distinguish two main groups - tweeters(HF) and woofers(LF). As for the representatives of the first group, they, as a rule, represent the most common (popular) search queries that are found in a particular area. Low-frequency users, on the other hand, are words or phrases that, in comparison with high-frequency users, are much less common when Internet users compose search queries on a particular topic.

Thus, the presence of two main groups of keywords determines two basic strategies search engine optimization web portal regarding the use of keywords. The first of them involves the introduction of a relatively small number of high-frequency keywords into the thematic content of the site. The second, on the contrary, provides for filling the text material of the web resource with numerous low-frequency search queries.

Of course, in our opinion, it is difficult to give preference to any one strategy in the process of search engine optimization, and that is why, as practice shows, experienced webmasters or SEO-optimizers, when promoting their Internet brainchild, resort to the services of both.

And yet, in some cases, according to experts, it is worth giving preference to any one strategy. For example, if we are talking about a young, recently launched project on the network, then in this situation it is recommended to fill its thematic content in line with the second strategy - an abundant number of low-frequency players. Why, you ask? The answer is quite simple: according to statistics, it will be quite difficult for such a resource to “compete” in the competition with already popular websites of the same subject, which in the structure of their texts use just high-frequency words and expressions and are in the first roles in the rankings of search engines. However, if you resort to the second strategy and introduce into the content of a young site large quantity low-frequency users, then the optimizing effect can exceed the wildest expectations - for such keywords, the resource can quickly get to the leading positions of search engines.

Summing up, I would also like to draw the reader's attention to the fact that it is possible to find out which group a particular keyword or phrase belongs to in the mainstream of a specific topic thanks to specialized Internet resources (of which there are a huge number of them nowadays - for example,) , as well as thanks to the separate services of the search engines themselves (for example, Yandex -, Rambler -, and Google -

Today's article will be about search queries. And, as you may have guessed from the title ;-), there are 4 types - long tail, low-frequency, mid-frequency and high-frequency.

You will also learn what the advantages and disadvantages of these queries are, and which keywords are the best to rank for.

Types of search queries:

Long tail Is a search query that is very rarely requested by the user (1-10 times a month). In other words, a long tail is also called a Long tail query. I will give an example of such requests:

  • buy a laptop in an online store inexpensively on credit;
  • how to create a website yourself for free step-by-step instruction video;
  • buy chinese phones wholesale in Odessa;
  • buy a 22-inch samsung TV in Moscow;
  • how to make money on the Internet without a website.

I checked each of these requests at wordstat.yandex.ru. It turns out that Yandex shows them to visitors no more than 10 times a month.

Despite such a low number of impressions, I believe that it is imperative to use them when selecting keywords.

Firstly, if a visitor comes to the site on request, for example, "buy Chinese phones in bulk in Odessa", he will buy Chinese phones in bulk, and in Odessa: smile :. These keywords are used by the most targeted visitors, who, in most cases, become buyers.

Secondly, there is practically no competition for long tail queries, and it is very easy to get to the TOP. To do this, it is enough to enter such a request into the article once and put several internal links with this one.

Well, and thirdly, 60-90% of all visitors come to the site for such requests. Yes, you may be surprised and disagree with me, these dummies, as many call them, give more than half of the search traffic.

I'm not saying that you need to create a special page to get to the top. You don't need to do this. But such a tail can be added to the main query. For example, you are promoting on the request how to make money on the Internet. So why not write once in an article how to make money on the Internet without a website. This is very easy to do, and there will be a lot of sense from it. I also advise you to read the article: "?" In this article, you will learn where to look for such queries and how to correctly enter them into the text.

Low-frequency requests (LF)- these are requests that have low competition and are rarely requested by users. For example, here are some low-frequency queries:

  • buy chinese tablet online store;
  • plastic windows in Moscow are cheap;
  • buy chainsaw oil calm;
  • repair in an apartment with your own hands where to start.

Do not confuse low-frequency queries with a long tail. Woofers differ from long tail in that they have more impressions per month. In most cases, it is very easy to reach the top for such queries. To do this, you need to create a special page and write a large article tailored for this request. Then you can also add several links from others internal pages, or buy several links on other thematic sites.

But there are also situations when low-frequency queries are highly competitive. This sometimes happens in highly competitive commercial niches. Therefore, you should always analyze each request and look at the sites that are in the top for it.

The advantage of these queries is that visitors go to the target site and in most cases become buyers when it comes to commercial niches. The main disadvantage is that very few people come to them and bring the site only for low-frequency queries, it is very difficult to get high traffic from search engines.

Medium Frequency Requests (MF)- these are requests that are requested by visitors from about 1,000 to 10,000 times a month. This number will be different for each niche. Here are a few medium-frequency queries as an example:

  • how to make money on the Internet without investments;
  • kitchen knives;
  • buy plastic windows;
  • what is music;

Many people think that medium-frequency queries are necessarily medium-competitive. In most cases it is, but not always. For example, take two queries: “what is music” and “buy plastic windows”. Although these queries are mid-range, it is still much more difficult to move to the top in the second than in the first. This is due to the fact that the first request is informative, and the second is commercial. And since commercial inquiries bring money, there is a lot of competition for them. This once again suggests that first of all, you need to take into account the competition, and only then the number of impressions.

Medium-frequency queries are like a sweet spot and it is imperative to move along them. They will bring a lot of visitors, and it is also quite possible to get to the top.

High Frequency Interrogations (HF) Are those requests that are requested by users the most times. As usual, I will give an example of such requests:

  • notebook
  • music
  • plastic windows
  • Yandex.

The main advantage of these queries is that they are able to bring the largest number of visitors to the site from. But here is their drawback - they are very competitive, and to get to the top on them, you need to spend a lot of time and money.

Also, I don't like to rank for high-frequency keywords because they have a very low conversion rate. For example, a visitor enters the word "laptop" into a search engine. I don't understand what he is looking for. He wants to buy a laptop, or look at prices. Or he can read the information or see photos of laptops: smile :. Thus, the page may be one thing, and the visitor is looking for something completely different. Also, one that is in the top for a high-frequency request will be larger than, for example, a page that is in the top for a low-frequency request.

What are the best keywords to promote

In short, it is best to promote all requests at once, and it does not matter if the site is one day or 10 years old. I will now explain why I think so. See, for example, we have 4 requests.

  1. Long tail - how to create a website yourself for free without registration; (6 views)
  2. Low-frequency query - how to create a website yourself for free; (370 views)
  3. Medium-frequency query - how to create a website yourself; (2022 impressions)
  4. High-frequency request - site. (15 859 views)

It makes no sense to create a page for the long tail, since we will get very few visitors. Our website Yandex will show only 6 times a month, believe me, this is very little: smile :.

It is also not worth promoting on the request "site". Firstly, there is a lot of competition, and secondly, this is not a targeted request and we will get a large bounce rate. It remains to choose a low-frequency or high-frequency request... Both of these options are good, but it’s best to go for all of these queries at once.

To do this, we can simply combine all these requests into an ode phrase - "how to create a site yourself for free without registration", and write this phrase in the headings, several times in the article and in the url of the link. For a complete set, you can also add some subtitle to the ALT tag. Can be affixed internal links with the anchor of this passphrase.

After a while, the long tail and low-frequency query will hit the top if you write a good article. Medium-frequency query can be forgotten in the top by external links. As for the tweeter, you need to look at what position it is. If you reach at least the top 30, then you can also promote with external links... Only there will be a lot more links like this: smile :.

If you use this keyword selection scheme, then you will get a lot more visitors to your site from search engines. Many may ask, "What if you can't combine all the queries?" If it doesn't work, then you can combine at least mid-frequency and high-frequency or low-frequency and Long tail queries, etc. Sometimes I manage to combine 6 queries into one phrase that can be easily entered into an article. The main thing is to spend more time on the selection of keywords and it is better to select words for a separate article, and not for the whole site at once, because if you select for the site, you can get confused: smile :.

That's all for me. I thought to briefly describe the types of search queries - long tail, low-frequency, mid-frequency and high-frequency, but it turned out, as always, much more ;-).

A search term is what a user enters into a search:

The frequency is largely due to the topic and area of ​​the business, as well as the region, seasonality and search engine.

You can check the frequency using Yandex.Wordstat.

Types of search queries by their frequency

  • How to find low-frequency queries? Take everything that Wordstat shows, up to 1 impression per month. The more bass at the start of work, the more traffic there will be.
  • How to promote low-frequency queries? These are the simplest and most undemanding queries, they do not need to be backed up with links - you just need to create relevant content: write articles, news, product cards that will answer the user to his question as meaningfully and accurately as possible.
  • Traffic for such requests will start to grow immediately, but perhaps slowly: the requests are low-competitive, the results may not be impressive at first, but the more such requests are introduced to the site, the higher its traffic will eventually be.

Highly competitive low-frequency requests do occur, but rarely - mainly in narrow commercial niches with high competition. That is, there are very few people who enter such requests, it will not be easy to bring the site to the top, but if a user comes to your site, then most likely he will become a buyer.

Medium-frequency requests, their concept and features

How many mid-frequency queries are? The midrange is slightly more popular than the bass. Medium-frequency and low-frequency queries are the basis of website promotion, because there are the most of them. Using both groups of queries, you can achieve optimal traffic with a small investment.

It is more difficult to promote a site in commercial mediums than in informational ones, and this must be taken into account: commercial requests are selling ones, and the competition for them is higher. For medium-frequency requests, the number of offers corresponds to the level of demand: there are indeed a lot of sites that are promoted mainly in the midrange. For example, on the Internet, more than one company offers "Buy plastic windows inexpensively", so be prepared that the work on the site in this case can take a lot of time.

High-frequency queries, their concept and features

What queries are considered high frequency? Those that users enter in the search most often - more than 1000 times a month, for example:

High-frequency queries are an as wide variety and total number of options as you like: here are not only informational and commercial, but also branded queries, which generate a lot of traffic. But such queries are extremely highly competitive, so the highest frequency queries are the most expensive in all respects.

Another drawback of high-frequency queries in Yandex and Google is not the highest conversion: it is not clear what the user wants by entering into search string inquiry "Laptop screen"... He needs information on care, addresses of workshops where he can be repaired or replaced, or some specifications? And the content of the page may not be what he is looking for at all.

  • How to determine a high-frequency request or not? Use all the same Yandex.Wordstat.
  • How to promote high-frequency queries? Long and expensive. To get to the top of the search results, you will have to work long and hard on the site, investing heavily, including financially. It should be borne in mind that, in particular, the highest-frequency queries (Yandex or Google - it doesn't matter) are a huge flow of audience, including non-target ones, and extremely high competition.

What are the best queries to choose for promotion?

What queries - low-frequency, medium- or high-frequency - to collect for search engine optimization of your Internet site? The ideal promotions are low-frequency and highly competitive, but this is a seldom-fulfilling optimizer and client's dream. Therefore, which queries are best for your site depends on the site itself.

If SEO has not been carried out earlier, the site is not optimized and you are only at the beginning of the journey, then you need to take on the low frequencies first and work on them, gradually connecting the midrange and high frequencies.

If your site is optimized for midrange and bass as much as possible, go for high frequency.

By the optimization vector, you can also select queries for promotion:

  • if the site is developing for demand in a direction or area as a whole - use HF;
  • if you need to attract targeted visitors who are looking for one or more areas of your company's work, use more midrange;
  • if you need high conversion and sales growth, focus on low frequencies.

/ Date: 2014-07-30 at 22:35

Hello friends, everyone. In this article I will tell you about what LF, MF and HF are, how these letters are generally deciphered in the Seo environment and how the frequency is generally determined.

The topic of website promotion touches upon a lot important points which every budding webmaster should be familiar with. One of those moments - keywords, which are an important part of every site.

Keywords, which some webmasters also call keys and keys, are words and phrases that users usually type into a search to find information on a given topic.

I've mentioned them many times in previous articles, introducing you to the basics of SEO, so it's time to tell you about keywords in more detail, teaching you how to work with them.

Why is it important to optimize your articles for COP?

I also talked about the fact that the site should be optimized for key queries. Each site has a lot of pages, this is the main page, and sections of the site, as well as articles posted in these sections, and all of them must be optimized for a specific key.

Let's dwell on this point and try to understand why it is so important to optimize all the content on the site for certain keywords. I will try to explain this with a specific example.

Let's say you have a site on a construction topic, which has an article "How to build a house from a brick", optimized for this key. In this article, you describe in detail the process of building a house.

Will the user get an answer to their question? Yes. And now the situation is different. The same article, optimized for the same key, but telling about some company engaged in the construction of brick houses.

Will the user get an answer to his question in this case? No, and most likely he will immediately close your site, and the reason for this will be the wrong keyword. And further search engines noticing that visitors have no interest in this article, they will conclude that your article does not belong in the TOP, lowering it in the search results.

It is for this reason that you need to correctly select keywords for each article on the site. Therefore, try to write articles for certain key queries and reveal the whole essence of this issue.

Also, do not optimize an article for several keys at once, as this will not achieve anything. Choose 1-2 keywords that are related to the content of your article, and that will be enough.

What types of key queries exist (LF, MF, HF), how they are deciphered and how they differ from each other.

I have also said that keywords can be classified into low-frequency, mid-frequency and high frequency.

High-frequency queries (HF) include the most popular queries that are searched for by a large number of users. Let me give you an example. The key phrase "DIY construction" is a high-frequency query. It does not bear any specifics and is for informational purposes only on this topic.

The key word “building a house with your own hands” can be attributed to the medium-frequency query (MF). This query is more specific, but far fewer people are looking for this query.

If users want to get more specific information, then they enter low-frequency questions (LF), for example, the key phrase "building a brick house with your own hands."

The differences between each of these types of keys are obvious: the lower the frequency of the request, the less competition, and the shorter the key, the higher its frequency.

As for articles, as a rule, they are written for low-frequency queries, since the main purpose of each article is to give the user specific information on the issue of interest.

Mid-frequency keys can be used to optimize sections of the site, as they clarify in more detail what the section is about, but still do not give specifics. Well, high-frequency keys, in turn, can be used for optimization home page by informing search engines and visitors about the theme of your site.

And to make it clearer for you, I drew the following diagram for clarity:

How to determine the frequency through Wordstat yandex and Allpositions

The next thing I would like to tell you about is the definition of the frequency of keywords. This is necessary in order to select the most frequent queries for your site. I will tell you how to determine the frequency of keywords using the example of services such as Wordstat yandex and Allpositions.

Let's start with Wordstat... I enter the keyword I'm interested in and see the following:

Many beginners believe that 38565 is the frequency of this key. But this is not so, and Wordstat just dumped us general statistics for all keywords in which this phrase occurs. To find out the exact figure of the frequency of our request, you need to enclose it in quotes:

The number 112 is the real frequency of this key. At first glance, a seemingly high-frequency query turns out to be quite different in practice. In this way, you can filter out keywords when compiling a semantic core.

You can also make a selection by region if you are promoting a site in a specific area or city.

Now let's go to the service Allpositions... In fact, this service is designed to check the positions of your site in the search engine, but you can also find out the frequency there. You will need to register first.

I will not dwell on this step, since registration is quite simple. After registering and logging in, you will be prompted to create a project:

Enter your website address in the URL field and click add. After that, you will need to create a report:

This will not cause you any difficulties. There you will need to enter the site address again, select the search engines and regions for which the site will be promoted and set the time at which the positions will be checked. After the report is drawn up, you need to add the keywords by which the site is promoted:

Enter the keys you collected and add them. After that, you will see the following sign in front of you:

In fact, there is another column in which the keywords are entered, but since I used them from my site, I will not advertise them. Wait a while for the report to update, after which you will see statistics for each keyword:

So in the frequency column, the frequency of each key is displayed.

How to use query languages ​​in Wordstat yandex correctly

And the last thing I would like to talk about is the query languages ​​in Wordstat yandex. I have already mentioned one of the query languages ​​above, talking about checking the frequency key request in wordstat, so that's where I'll start.

Quotes. They are needed in order to find out how many times a particular request was entered. Quotes help exclude other queries that include your keyword. If you need to exclude a word and collect keys that do not contain it, then this can be done using the minus. Note:

These are queries without a minus, but here's how the statistics will change if you add it:

Since there is a minus request, then, probably, there is also a plus request? Yes, there really is such a request, and it is intended so that the statistics take into account requests with prepositions and conjunctions:

As you can see, in the second case, only those queries that contain the phrase "for home" are displayed.

Another request is Exclamation point"!" It is necessary in order to select all queries in which the key you need is present:

And the last of the operators in the query language is for grouping keywords. It is denoted by brackets "()" and a vertical bar "|" inside brackets between words:

That is, we made a request so that wordstat would give us the keywords for the queries “house renovation” and “house construction”.

So we covered everything that is important to know for working with keywords. I hope you find this article helpful and make it much easier for you to find keywords for your site. All bye and see you soon.

Sincerely Shkarbunenko Sergey

Fitting © 2021 Tech Look - Gadgets. Android device. Antiviruses. Security. Graphics. Internet. Mobile devices