MongoDB ObjectID Generator

How to generate a MongoDB ObjectId

1. Set how many ObjectIds you need. New values appear immediately — there is no button to press and no request to a server.
2. Copy any single value with its copy control, or copy the whole batch at once for a seed file.
3. Paste an existing 24-character ObjectId into the decoder to read back the timestamp embedded in its first four bytes.
4. Every value is generated by your browser's cryptographic random number generator. Nothing is transmitted, so the IDs you generate are known only to you.

Why use MongoDB ObjectID Generator?

• 100% free with no limits, no sign-up and no watermarks.
• Private by design — your data are processed in your browser and never uploaded to a server.
• Fast and lightweight, with instant results even on a phone or a slow connection.
• Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
• Part of a full generators suite, so related objectid tasks are one click away.

What people use MongoDB ObjectID Generator for

• Creating a valid MongoDB _id by hand for a seed script, a fixture file or a migration.
• Generating a test document identifier without connecting to a database or starting mongod.
• Reading the embedded timestamp out of an existing ObjectId to find when a document was created, without querying the collection.
• Producing an object id generator output to paste into a REST client while testing an endpoint that expects a real _id.
• Making stable identifiers for a Mongoid or Mongoose fixture, where the same 12-byte BSON value has to appear in two places.
• Checking whether a 24-character hex string is a plausible ObjectId before writing a validation rule for it.

MongoDB ObjectID Generator: limits and things worth knowing

• An ObjectId is 12 bytes shown as 24 hexadecimal characters. The layout is a 4-byte Unix timestamp in seconds (big-endian), then 5 bytes of random value generated once per process, then a 3-byte counter that starts at a random value and increments.
• The first four bytes make ObjectIds sort roughly by creation time, which is why sorting by _id is the common substitute for sorting by createdAt. The resolution is one second, so documents created within the same second are ordered by the counter, not by real time.
• You can extract the creation time yourself: take the first 8 hex characters, read them as a base-16 integer, and treat the result as a Unix timestamp in seconds. In JavaScript that is `new Date(parseInt(id.slice(0, 8), 16) * 1000)`.
• An ObjectId therefore LEAKS its creation time to anyone who sees it. If a document id is exposed in a URL, so is the moment the record was created — which is fine for most applications and a real disclosure for some. UUID v4 leaks nothing by comparison.
• ObjectIds are not secrets and must never be used as one. The counter is sequential and the timestamp is predictable, so an attacker who sees one id can guess nearby ones. Use a random token for anything that grants access; use an ObjectId for identity.
• The older specification described a 3-byte machine identifier and a 2-byte process id in the middle bytes. That was replaced by 5 random bytes in MongoDB 3.4, and a great deal of documentation elsewhere on the web is still wrong about this.
• Generating an ObjectId on the client is normal practice, not a workaround. The official drivers do exactly this — they construct the id locally and send it with the insert rather than asking the server to mint one, which is what makes optimistic inserts and offline writes possible.
• Mongoid, the Ruby ODM, uses the same BSON ObjectId type, so a value generated here is valid in a Mongoid fixture, a Mongoose seed and a mongosh script alike.
• Every mainstream driver can build one directly: `ObjectId()` in mongosh, `new ObjectId()` from the Node `mongodb` package, `bson.ObjectId()` in PyMongo, and `primitive.NewObjectID()` in the Go driver.
• MongoDB adds an _id of this type automatically when you insert a document without one, and indexes it. Supplying your own is only necessary when you need to know the id before the insert returns.

Sources

• BSON ObjectId specification (bsonspec.org)
• MongoDB Manual — ObjectId
• MongoDB Manual — _id field and default index

Is it private and secure?

Your privacy is built in. MongoDB ObjectID Generator runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

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