What's Inside a 3,000-Site Username Checker? We Opened Ours

Username checkers love big numbers. Ours says it checks 3,450+ sites, Maigret's database lists over 8,000, and Sherlock and Blackbird list several hundred each. Those numbers are true, but they don't tell you what you most want to know: will it find the accounts that matter? So on October 26, 2026 we opened our own site list and counted what is actually in it.

A username checker is a tool that tests whether a username exists on many websites at once, by asking each site for that name's profile and reading the answer.

The breakdown: 58 big platforms, 3,399 smaller sites

Our engine sorts every site into one of three tiers. Here is how the 3,457 sites split on October 26, 2026:

Tier	Sites	Share	Examples
Major platforms	58	1.7%	YouTube, X, GitHub, Twitch, Roblox, Pinterest, Steam
Niche sites	1,004	29.0%	Hobby, gaming, art and developer communities
Forums and fediverse servers	2,395	69.3%	Mastodon servers, Discourse forums, PeerTube sites

By topic, 2,832 sites are social (82%), 454 are video, 52 are code hosts, 33 are gaming and the rest are blogs, music, art and shops.

Why 91% of sites share ten rules

Most of the list is a small number of open-source programs that thousands of communities run on their own servers. Each program shows profiles the same way, so one rule checks every server that runs it:

Software	Sites in our list
Mastodon	1,441
Discourse (forums)	586
PeerTube (video)	447
Misskey	395
Lemmy	111
Pleroma	73
MediaWiki (wikis)	55
Gitea (code)	20
Mbin, Flarum, XenForo	5
Own rule (custom)	324

Mastodon, Misskey, PeerTube, Pleroma, Lemmy and Mbin are all part of the fediverse, the network of independent social servers. Together they make up 2,470 of our sites, 71% of the list.

Where the sites come from

We did not copy another tool's list. Sites were added from public directories that list live servers, then each one was tested before it went in:

• 1,376 from the public list of servers known to the lemmy.world fediverse server
• 517 from Discover Discourse
• 445 from the JoinPeerTube directory
• 393 from the Misskey server list, 279 from joinmastodon.org, 56 from MediaWiki
• 69 popular sites picked from the Tranco top-sites ranking
• 297 added by hand, mostly big platforms, with rules written and tested one by one; about 25 more from the platforms' own developer docs

What the site count really tells you

A large number is good for one job: finding someone's accounts on small communities, which is often where old or forgotten profiles live. It says little about the big platforms, because every serious tool covers those. For those, two things matter more than the count:

1. Does the check still work? Big platforms change their pages and block automated checks. Our nightly site health tracker shows that on October 26, 2026, a few big platforms, TikTok, Instagram and Discord among them, were refusing our server's checks.
2. Does it give false positives? In our benchmark of four tools, a handful of broken rules caused most of the wrong "found" results, whatever the size of the list.

The other tools' lists are built the same way. In our October 25, 2026 run, Sherlock checked 412 sites, Blackbird 692, and Maigret scanned its default top 509 out of a database of 8,232. A bigger database doesn't mean more of the sites you use.

Worked example: what a search for nightowl92 covers

Say you search nightowl92 with the full scan. The engine asks all working sites at once. The big platforms answer first and matter most: you read those results line by line. The thousands of Mastodon and forum servers mostly come back Not found, and the few that say Found are worth opening, because a match on a small server is more likely to be the same person. Instagram and Threads aren't checked automatically; their checker pages show how to check them by hand.

How we counted (October 2026)

• Source: our engine's own site database on October 26, 2026 (3,457 sites). We publish counts only; the detection rules stay private.
• Tiers and software: as recorded for each site when it was added and tested.
• Other tools: the site counts each tool reported in our own run on October 25, 2026, with default settings.

Limitations

• Tiers are our own labels. Another tool might call some of our niche sites major, or the reverse.
• The list changes every week as servers close, new ones open and broken rules are fixed.
• We counted what is in our list, not which sites people search most.

Frequently asked questions

Is a checker with more sites better?

Only for small communities. For the big platforms, check how recently the tool tested its rules and how many false positives it gives.

Why are so many of your sites Mastodon servers?

Because there are thousands of them, each with its own users, and a single rule checks them all.

Can I see the list of sites?

The supported sites page lists the sites by name and category. The detection rules themselves are not published.