Definition
The site quality index (SQI, in Russian ИКС, индекс качества сайта) is a number Yandex calculates for a whole site to show how useful it is to its users. It replaced the older thematic citation index (тИЦ) in 2018. Yandex says it looks at the size of the site's audience, how satisfied users are with it, and how much users and Yandex trust it. The exact formula is not published, and Yandex recalculates the value from time to time.
Why it matters
SQI is a summary of how Yandex sees your site over time, not a setting you can change directly. A rising value usually follows more visitors who find what they came for. A sudden drop is worth a look at the site problems Yandex reports and at how many pages are excluded from search. It matters most if part of your audience searches with Yandex.
Where to see it
Add and verify the site in Yandex Webmaster first; see add a site to Yandex Webmaster. Yandex Webmaster then shows the current SQI on the site's summary and its history among the site's quality indicators. If Yandex answers HOST_NOT_LOADED, it has not loaded the site's data yet; see Yandex HOST_NOT_LOADED.
Ask mowteng
With Yandex connected on the account page (optional and still experimental), yandex_site_summary returns the SQI together with pages in search, excluded pages and the site problems Yandex reports by severity. More on the Yandex Webmaster MCP server page.
What is the Yandex site quality index of my site right now, how many pages are excluded from Yandex search, and which site problems does Yandex report?