Google has no documented limit on the number of characters for the new site name as listed in Google Search. In fact, the documentation says "there's no limit to how long a site name can be" but Google does recommend being concise with the name.
Google also said that the site name can be trimmed differently based on the device loading the search results. Google wrote, "on some devices long site names may be truncated." Google supports an alternative site name for those cases, "if you have an alternate name that's commonly recognized, you can use the alternateName property to specify that name (for example, an acronym)," Google explained.
In short, Google recommends that you use a concise, commonly-recognized name for your site name.
John Mueller of Google was recently asked about this on Twitter and said "AFAIK there is no fixed & documented limit, I'd focus more on the room that the average phone gives you (and usually a name is short & sweet anyway)."
AFAIK there is no fixed & documented limit, I'd focus more on the room that the average phone gives you (and usually a name is short & sweet anyway).
— 🦇 johnmu: cats are not people 🦇 (@JohnMu) October 23, 2022
Now, this should not be a huge surprise. Google has changed the display length of the title tag numerous times and always said the length does not matter. Google has said there is no fixed title tag length. The display of a snippet is not directly related to what Google uses for ranking purposes.
Forum discussion at Twitter.
