dc=tools
Paste a SID in any form to get every other form and a filter that finds the object. Everything runs in your browser, so nothing you paste leaves your machine. The page's Content-Security-Policy also stops it from sending anything, which you can check in its source.
Paste the S-1-5-… form, hex, base64 from an LDIF export, or the escaped form from a filter. Active Directory also accepts the S-1-5-… form directly in a filter. Other servers and some tools need the escaped bytes.