Traffic can sink for various reasons. Perhaps you have changed something on the site or, on the contrary, did nothing, and there were fewer visitors. In any case, this should be an explanation. Perhaps the visitors do not find what they were looking for, or the search engine algorithm has changed, or anything else. Consider the possible nuances of sagging traffic.
Source. From which source did visitors come from? With context, organic search, image search? See if everything is in order with the display of images, if there are problems with the descriptions, whether they are accessible to search engines (for example, they can be closed from indexing in robots. Txt).
From which search engine traffic fell? If a drop was detected from all search engines, then the problem is most likely in the site itself, in its technical good condition. For example, the cause of subsidence is often unavailability at the time of reindexing, problems with headers and snippets, incorrect server response (all pages should give "200 OK"). If we are talking only about one search engine, then we can say that its algorithms have “bothered” about the site. That is, it does not meet the quality criteria of a particular search engine.
Places on the site where people go. Usually the resource is divided into sections. So, he, as a rule, has the main, subsections, perhaps there is a catalog of goods, etc. If you understand how the traffic “flows” through your site, you will be able to establish the reason and narrow the search. So, if the traffic disappeared only to the main page, and other pages remained visited, then the problem is most likely only with the home page. By the way, advertisers often use such a trick: they show only a general picture of visits, but do not say that most of them fall on any one part of the site, while the rest of the pages and sections are empty.
A bot or a person? Even if you are not booting traffic with bots, competitors can do it for you. Look in the analytics systems if there are any sharp jumps in the upward transitions. If there is, and at the same time, the conversions on the site remained unchanged, it is possible that you are added to the "dead" visitors. Because of this, behavioral factors suffer, which in turn leads to a decrease in the site in the issue, the imposition of filters.
From which devices is the traffic? The webmaster can monitor the site from one place (for example, from a stationary computer), but people still use different mobile gadgets and tablets. Look at whether the mobile version is in place, whether it has "flown away", whether the quality of traffic has decreased from one or another device (time of visit, depth of views, etc.). Always make sure that all categories of users are comfortable viewing your site.
From which browser how much traffic? Keep track of the ratio of visits from different Internet browsers. See why there are more visitors from one browser, and less from another, are there any changes, traffic jumps in this analytics segment.
What is the purpose of incoming users? It is important to understand why a person comes to you. It should be realized that the faceless word "traffic" means completely live visitors, and each of them comes for a certain help. Determine the needs of your target audience in order to improve behavioral factors.
The analytics in this case should be divided into segments:
Low-frequency request, as a rule, drops out of the search due to the overall poor quality of your resource. A drop in a high pass report is often associated with re-spam. If pages with commercial inquiries subside, then it is already a matter of changing the algorithms; if regional traffic falls, you need to look at whether there is a problem in determining regionality.