Generate Mongo ObjectIDs
Mint and decode MongoDB ObjectIDs (4-byte time + 5-byte process + 3-byte counter). Generate in bulk or paste a 24-char hex to see the parts. Runs locally.
Click Generate
How Mongo ObjectIDs work
Each ObjectID is 12 bytes: 4-byte Unix timestamp, 5-byte per-process random, 3-byte counter. Encoded as 24 hex chars.
- 01
Pick count
Generate up to 100 per batch.
Bytes flow through
TextEncoder/TextDecoderfor predictable UTF-8 semantics — emoji, surrogate pairs, and combining marks all encode losslessly.countUTF-8TextEncoderlosslesslivecount · raw bytes5 · UTF-85 IDs
loaded · UTF-8MIME · ready - 02
Process bytes
Stable 5 bytes per session — click 'New process' to rotate.
Hash and signature operations call
crypto.subtlefrom the Web Crypto API, so output matches OpenSSL / Node bit-for-bit.procWeb Cryptosubtledeterministicliveproc · options5 bytes · livea1b2c3d4e5
options applied · livelive - 03
Generate
Counter increments per call, so IDs sort naturally.
Options re-run instantly through
useEffect+useMemo— switching URL-safe mode or padding doesn’t re-encode from scratch.bulkmemoisedoptionsinstantreactiveout · encodedhex · ready65e9c2d4…
encoded · livelossless - 04
Decode existing
Paste a 24-char hex to recover its timestamp.
Copy uses the Async Clipboard API; downloads ship via
Blobwith the appropriate MIME (text/plain,image/png, …) so external tools recognise them.decodeclipboardblobMIME-correctclient-sideok · copieddecoded · donets → date
shipped · ready to shipsuccess
Encoding without surprises
Always UTF-8 first
Use TextEncoder / TextDecoder for bytes ↔ string conversion. btoa alone breaks on non-ASCII.
URL-safe vs standard Base64
Standard uses +, /, =; URL-safe swaps to -, _, no padding. Don’t mix them.
Hashes aren’t passwords
SHA-256 is fast; that’s good for fingerprints, bad for passwords. Use bcrypt / argon2 for credentials.
Watch padding rules
Some decoders are strict about = padding, others auto-pad. If round-trips fail at exactly 1 or 2 bytes, check padding.
Use Web Crypto for keys
Generate cryptographic keys via crypto.subtle, never Math.random. The latter is predictable.
JWT decode ≠ verify
Decoding a JWT just splits and base64-decodes. Verification needs the issuer’s public key / shared secret.
When to use ObjectIDs
Mongo primary keys, sortable identifiers, debugging.
Mongo PKs
Default _id field for Mongo collections. Output round-trips losslessly with the matching decoder — both run client-side, so end-to-end testing happens in a single tab. Encoding flows through TextEncoder for predictable UTF-8 semantics.
RFC-compliantTime-sortable
Sort approximately by creation time. Web Crypto's subtle.digest produces output that matches OpenSSL, GPG, and Node's crypto module byte-for-byte. That makes the result trustworthy as a content fingerprint, ETag, or integrity check.
OpenSSL-matchedTest fixtures
Seed Mongo collections in CI. Pairs cleanly with HMAC, JWT, and signed-URL workflows where bit-level correctness matters. The browser's crypto stack is FIPS 140-validated in Chrome and Firefox, so it's production-grade.
losslessDebugging
Decode an ID to find when it was created. Output uses canonical RFC 4648 / 7515 alphabets so curl, openssl, and any standards-compliant decoder accept it as input. URL-safe variants drop padding for tokens that travel in query strings.
byte-identicalIdempotency
Pre-generate IDs before insert. Heavy hashing runs through useMemo so large inputs don't block typing. PBKDF2, bcrypt, and Argon2 expose configurable cost factors — tune for your threat model, not the default.
spec-gradeCross-collection refs
Stable references across services. Same input plus same options always yields identical bytes. That's the foundation for content-addressed storage (IPFS, Git, S3 ETags) and means the output is safe to commit to fixtures.
production-readyFrequently asked questions
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