Check if a CSDN username is taken

What we check on CSDN

Instant tier for username lookups - answered in well under a second

CSDN is checked from a username. The response says whether that handle exists on CSDN - registered: true or registered: false - with the moment that was established in checkedAt. An email address on its own cannot reach CSDN; if you only have an email, its local part is tried as a handle and any hit is labelled as derived, never counted as a confirmed match.

CSDN is in the instant tier: with ?instant=true it is among the first platforms answered, in well under a second. On a full lookup it is checked alongside every other platform and streamed as it lands.

If CSDN blocks the check, times out, or answers ambiguously, it is omitted from results[] entirely rather than returned as registered: false. Absence from the response means "unconfirmed", never "no account".

Who checks CSDN accounts

Developer accounts are checked by SaaS, cloud and API businesses that give away free trials, credits or compute. A real developer usually has years of history on code hosting and developer communities; an address that exists nowhere in that world, signing up for free GPU hours, is a classic trial-abuse pattern.

More on this: Signup fraud prevention.

Inputs CSDN accepts

• Username: send the handle as query. CSDN is checked for that exact handle - useful when a person reuses the same name across platforms.

One request

curl -X POST "https://api.digifootprint.dev/v2/lookup?wait=true" \
  -H "Authorization: Bearer dfp_your_key" \
  -H "Content-Type: application/json" \
  -d '{"query": "someuser"}'

What a CSDN result looks like

{
  "platform": "csdn",
  "registered": true,
  "checkedAt": "2026-10-15T09:53:16.095Z",
  "identity": "username"
}

The full response shape - breaches, web mentions, matches versus socialMatches, and what method means - is in running a lookup.

Related platforms

Every one of these is checked in the same request as CSDN.

More developer platforms: Pastebin, CodePen, GitLab, Codecademy, Kaggle, Hacker News · all developer

CSDN lookup FAQ

Can I check a phone number on CSDN?

Not directly. CSDN can be reached from username. Phone numbers are checked on the messaging and social apps that sign people up by phone.

How fast is a CSDN check?

Fast: CSDN is in the instant tier, so with ?instant=true it is answered in well under a second. A full lookup streams it as soon as it lands.

What happens if CSDN blocks the check?

CSDN is left out of the response. We never report a platform we could not confirm as "not registered" - a missing platform means unconfirmed, not absent.

Does the API return the CSDN account details?

No. You get whether an account exists for the input you sent, and when that was established. No profile contents, photos, followers or private data are collected or returned.