MongoDB ObjectId Generator

An ObjectId is the 12-byte (24 hex-character) identifier MongoDB automatically generates for a document's primary key (_id). The first 4 bytes are a Unix timestamp (seconds), the next 5 bytes are random, and the last 3 bytes are an incrementing counter.

In the Mongo shell or in code, ObjectId values are usually wrapped as `ObjectId("...")`. Picking this option produces the 24-character value already wrapped that way, so you can paste it straight into your code.

Yes. The first 8 hex characters (4 bytes) are a second-precision timestamp, so pasting a value into this tool's check field shows an approximate creation time right away. MongoDB itself relies on this property for time-range queries against _id.

Yes, the format is identical so it works fine. You don't normally need to set _id manually since the driver generates one automatically, but this is handy when you need specific values for seed data or migration scripts.

No. Every value is generated on the spot in your browser and is never sent to or stored on a server.