MongoDB ObjectId Decoder
Decode MongoDB ObjectIds into creation timestamps, random values, and counters. Build date-range query boundary ObjectIds from any date range.
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What is MongoDB ObjectId Decoder?
The MongoDB ObjectId Decoder is a free developer tool that splits 24-character hex ObjectIds back into their three components: a 4-byte Unix timestamp, a 5-byte random value, and a 3-byte incrementing counter. It also works in reverse — turning any date range into the boundary ObjectIds you need for efficient _id range queries. Everything runs in your browser.
Key Benefits
- Recover document creation times from _id alone, with no extra date field or index.
- Debug ingestion pipelines by verifying ID generation order and time windows.
- Build fast chronological range queries directly on the _id index.
- Bulk-decode hundreds of IDs and export results as CSV.
- Keep sensitive production IDs on your machine — the tool is fully offline.
Common Use Cases
- •Checking when a document was created from a support ticket that only shows its _id.
- •Estimating data distribution over time without scanning the whole collection.
- •Writing date-range queries against collections that only store _id.
- •Auditing whether two collections were written in the same time window.
- •Teaching and learning the internal structure of BSON ObjectIds.
How to Use MongoDB ObjectId Decoder
- Paste your ObjectIds: Copy one or more 24-character hex ObjectIds from MongoDB and paste them into the input box, one per line. ObjectId(...) wrappers are stripped automatically.
- Read the decoded table: Each row shows the creation time in your local timezone, the UTC ISO string, the 5-byte random value, and the 3-byte counter with its decimal value.
- Check the field breakdown: The detail panel splits the first valid ID into timestamp hex, unix seconds, random, and counter so you can see exactly how the 12 bytes are laid out.
- Build a range query (optional): Pick a from/to date below, and the tool generates the min and max boundary ObjectIds plus a ready-to-paste MongoDB shell query for that date range.
Key Features
- Decode creation timestamp, random value, and counter from any 24-hex ObjectId.
- Bulk decode: paste hundreds of IDs at once with per-row copy buttons.
- Export the full decoded table as CSV for spreadsheets and reporting.
- Build min/max boundary ObjectIds from a date range for fast _id range queries.
- Ready-to-paste MongoDB shell query generated from your date range.
- 100% client-side — works offline and never uploads your data.
Frequently Asked Questions
How do I extract the creation date from a MongoDB ObjectId?
The first 8 hex characters of any ObjectId are a big-endian Unix timestamp in seconds. Paste the ID into the decoder and it converts those bytes into your local date, the UTC ISO string, and the raw unix seconds — no database access needed.
What are the other bytes in an ObjectId?
Since MongoDB 3.4 the layout is a 4-byte timestamp, a 5-byte random value generated once per process, and a 3-byte incrementing counter. Older ObjectIds (pre-3.4) instead embed a machine identifier and process ID in the middle 5 bytes, but the timestamp and counter positions are unchanged.
Can I query MongoDB by date using only the _id field?
Yes. Because ObjectIds sort chronologically, you can convert your date range into min and max boundary ObjectIds and query with _id greater-than-or-equal and less-than operators. The boundary builder in this tool generates those ObjectIds and a ready-to-paste shell query for you.
Is my data uploaded anywhere?
No. All decoding happens locally in your browser with JavaScript. Nothing is sent to any server, and the tool works fully offline — perfect for decoding production IDs safely.