What exactly does this reproduce?

MONGODB-CR, MongoDB's original challenge-response authentication mechanism's underlying password hash: first md5(password) is computed, then that result is combined with the username and the literal string ":mongo:" and hashed again with md5. The specific construction is md5(username + ":mongo:" + md5(password)), and this tool computes that exact value.

Why fold the username into the hash at all?

Similar reasoning to PostgreSQL's md5 password format elsewhere in this category: mixing the username in means two different MongoDB users with the identical password won't produce the same stored hash, since the hash also depends on whose username it is. It's a weaker substitute for a real random salt (the username is public and often guessable), but better than hashing the password alone.

Is MONGODB-CR still used?

No, MongoDB deprecated MONGODB-CR starting in version 3.0 (2015) in favor of SCRAM-SHA-1 and later SCRAM-SHA-256, both proper salted, iterated authentication schemes. You'd only encounter this format today in old database exports, legacy documentation, or a system explicitly configured with --authenticationMechanism MONGODB-CR for backward compatibility.

Does this tool send my username or password to a server?

No. The hash is computed entirely in your browser using @noble/hashes, an audited JavaScript library, so nothing you type here is transmitted anywhere.

MongoDB Hash Calculator - Legacy MONGODB-CR Format Online

Overview

Introduction

Before SCRAM became MongoDB's default authentication scheme, MONGODB-CR used a specific double-md5 construction that mixed in the username, structurally similar to PostgreSQL's legacy md5 password format elsewhere in this category.

This tool computes that exact MONGODB-CR hash from a username and password you provide, entirely in your browser, useful for old exports or legacy MONGODB-CR-configured systems.

What Is MongoDB Hash Calculator?

MONGODB-CR's underlying password hash is md5(username + ":mongo:" + md5(password)), a nested double-md5 construction where the inner hash covers just the password and the outer hash mixes in the username and a fixed literal separator.

It predates MongoDB 3.0's deprecation of MONGODB-CR in favor of SCRAM-SHA-1/256, and is what a legacy export or an explicitly downgraded --authenticationMechanism MONGODB-CR setup would still use.

How MongoDB Hash Calculator Works

The password is first hashed alone with MD5, producing a 32-character hex intermediate value.

That intermediate hex string is then concatenated with the username and the literal separator ":mongo:" (username + ":mongo:" + innerHash), and the combined string is hashed again with MD5 to produce the final 32-character hex output this tool returns.

When To Use MongoDB Hash Calculator

Use this when working with an old MongoDB export, migrating a legacy MONGODB-CR-configured system, or studying MongoDB's authentication history.

Don't rely on this format for anything new; MongoDB itself deprecated it in 2015 specifically because SCRAM's salted, iterated design is meaningfully stronger.

Often used alongside Postgres Hash Calculator, MySQL Hash Calculator and Random MongoDB Hash Generator.

Features

Advantages

Exactly matches MongoDB's documented legacy MONGODB-CR hash construction.
The username-mixing design at least prevents trivial cross-user hash matching for identical passwords, unlike a bare md5(password).
Simple, deterministic, and easy to verify against a known legacy value or old export.

Limitations

The username is a poor substitute for a genuine random salt, it's public and often guessable, so it doesn't meaningfully resist a targeted attack.
MD5 is fast with no configurable work factor, unlike SCRAM's PBKDF2-based iteration count.
Deprecated by MongoDB since version 3.0 (2015); this format is now specifically a legacy/compatibility concern, not current MongoDB security practice.

Examples

Hashing a username and password pair

Input

username: alice, password: secret123

Output

a4e2bda49edab77384694dc8b58e4391

Computed as md5('alice' + ':mongo:' + md5('secret123')), the exact nested construction MONGODB-CR used.

Best Practices & Notes

Best Practices

Confirm the exact nested construction (inner md5 of password only, then outer md5 combining username, literal ':mongo:', and that inner hash) when reproducing this by hand.
If you administer a MongoDB system still configured for MONGODB-CR, plan a migration to SCRAM-SHA-256.
Never treat the username-mixing here as equivalent in strength to genuine random salting.

Developer Notes

Implemented as md5(UTF8(username + ':mongo:' + toHex(md5(UTF8(password))))) via @noble/hashes, matching MongoDB's documented MONGODB-CR construction exactly: an inner md5 of the password alone, then an outer md5 combining the username, a literal ':mongo:' separator, and that inner hash's hex string. Verified against a MONGODB-CR test vector (username 'alice', password 'secret123').

MongoDB Hash Calculator Use Cases

Reproducing a legacy MONGODB-CR password hash from an old database export
Debugging authentication on a system explicitly configured with --authenticationMechanism MONGODB-CR
Understanding MongoDB's pre-SCRAM authentication design during a migration
Comparing MONGODB-CR's username-mixing pattern against PostgreSQL's structurally similar legacy md5 format

Common Mistakes

Getting the nested construction order wrong, the inner md5 covers only the password; the username and separator are mixed in only at the outer hash step.
Assuming this format reflects current MongoDB defaults; version 3.0+ uses SCRAM-SHA-1/256 instead.
Treating the username-mixing here as equivalent in strength to genuine random salting.

Tips

If your target system is on MongoDB 3.0 or later with default settings, it's using SCRAM, not MONGODB-CR, confirm the configured authentication mechanism before assuming a match.
This category's Postgres Hash Calculator uses a structurally similar username-plus-password pattern if you want to compare the two legacy database credential formats.

MongoDB Hash Calculator