MongoDB ObjectId Decoder

How to use

1. 1Pick a layout: v4+ (default for every modern MongoDB driver) or v3 legacy for pre-2012 ObjectIds.
2. 2Choose a mode at the top: Decode single for one ObjectId, Decode batch for a pasted list, Build from date to invert the process, or Generate random to mint a v4 ObjectId on the spot.
3. 3Paste an ObjectId, paste a list of ObjectIds (one per line), or pick a date depending on the mode. Decoding runs on every keystroke and accepts ObjectId("...") and {"$oid": "..."} wrappers along with bare hex.
4. 4Read the timestamp, hex, mongosh and extended JSON forms, and the per-field values in the result panel. Use the copy buttons to lift any value, or Copy results as CSV in batch mode.
5. 5In Build from date mode, copy the produced ObjectId into a MongoDB query like _id: { $gt: ObjectId("...") } to fetch every document created after that moment without indexing a timestamp field.

About this tool

MongoDB ObjectId Decoder parses 12-byte MongoDB ObjectIds (also called BSON ObjectIds) and shows the embedded creation timestamp, the machine, process, random, and counter bytes, and every common wrapper form a developer is likely to encounter. Paste a bare 24-character hex string, an ObjectId("...") wrapper from mongosh, Robo3T, NoSQLBooster, or Studio 3T, or a {"$oid": "..."} extended JSON wrapper from a Compass export or a mongoexport file, and the tool strips the wrapper, normalizes the value to lowercase hex, and walks the bytes one field at a time. The default v4+ layout reflects the BSON specification update of September 2012 used by every modern driver (Node.js, PyMongo, Go, Java, .NET, Ruby, Rust, Swift) and by mongosh, Compass, Atlas, and Realm: bytes 0-3 are a big-endian 32-bit Unix timestamp in seconds, bytes 4-8 are a 5-byte random value chosen once per process, and bytes 9-11 are a 3-byte counter that starts at a random initial value and increments on each ObjectId. The v3 legacy layout still appears in archived databases and older tutorials and splits the middle bytes into a 3-byte machine identifier (the first 3 bytes of the MD5 hash of the host name) and a 2-byte process identifier; the process ID is shown in both big-endian and little-endian decimal because legacy drivers disagreed on the byte order. Each decoded ObjectId reports the canonical lowercase hex, the mongosh ObjectId(...) form, the extended JSON $oid form, the Unix seconds and milliseconds, an ISO 8601 UTC timestamp, a relative description (such as 3 years ago), every field decoded under the chosen layout with its hex bytes and decimal value, and a colour-coded 12-byte strip so you can see exactly which bytes became which field. A Batch mode decodes a pasted list of ObjectIds at once, counts how many parsed successfully, and exports the timestamps as CSV ready to drop into a spreadsheet or a query. A Build from date mode goes the other way: pick a calendar moment and the tool returns a representative ObjectId with the random and counter bytes zeroed, which is the standard recipe for the MongoDB range query db.collection.find({_id: {$gt: ObjectId("...")}}) that selects every document created after a given time without a separate index on a timestamp field. A Generate mode produces a fresh v4 ObjectId from the current second-precision Unix timestamp plus 8 bytes from the browser CSPRNG via crypto.getRandomValues, useful for test fixtures and seed data. Everything runs locally on your device, so the ObjectIds you paste here, along with any production identifiers they expose, never leave your browser.

Free to use. Works in your browser. No signup, no login.