Metadata section
Sits at the end of the file after a 14-byte marker. Holds the database type, build epoch, record size, node count, supported languages and description.
MMDB Reader
Open any MaxMind .mmdb database file, inspect its metadata and look up IP records as raw JSON. A full MMDB viewer that runs in your browser — your database is never uploaded.
Raw record
Load a database, enter an IP address, then look it up.
The record appears here exactly as it is stored in the file.
Parsed locally with WebAssembly. Your database file never leaves this page.
How to Read an .mmdb File
Load your .mmdb file
Drag a MaxMind DB file onto the box above or click to browse for one. The file is opened locally by a WebAssembly reader — it is never uploaded, so even a paid commercial database stays on your machine.
Check the database metadata
The reader immediately shows the database type, build date, IP version, record size and node count, which is the fastest way to confirm you shipped the build you meant to ship.
Look up an IP address
Enter any IPv4 or IPv6 address and get the raw record back as JSON — every field the database actually stores, with nothing hidden and nothing invented.
What Is an MMDB File?
MMDB is the MaxMind DB binary format — a single file that answers "which record covers this IP address?" in a few memory reads, with no database server involved. It is what free and commercial IP datasets alike are distributed as, and what the industry has standardised on. Three sections do all the work.
Binary search tree
Each IP address is walked bit by bit through the tree. IPv4 lookups start at the node reserved for the IPv4-mapped range, so both address families share one structure.
Data section
Separated from the tree by 16 zero bytes. Stores the actual records in a compact typed format — maps, arrays, strings, doubles and pointers that deduplicate repeated values.
Which MMDB Databases Work Here
Most online viewers decode records into a fixed City shape and quietly drop anything that does not fit. This reader returns the raw record instead, so an ASN file shows autonomous system fields, an Anonymous IP file shows its boolean flags, and a database you built yourself shows exactly the fields you encoded.
- City databases City, region, postal code, coordinates and time zone
- Country databases Country, continent and registered-country fields
- ASN databases Autonomous system number and network organisation
- ISP and domain databases Carrier, organisation and hosting domain
- Connection-type databases Cable, DSL, cellular, corporate or satellite
- Anonymous-IP databases VPN, proxy, Tor and hosting flags
- Proxy and hosting datasets Datacenter, relay and residential ranges
- Custom in-house builds Whatever schema you encoded yourself
Runs Entirely in Your Browser
Nothing is uploaded
The file is opened with the browser File API. It is never sent to nodedata.io, so a licensed commercial database stays on your machine and your queries stay private.
Real MaxMind DB parser
The lookups run through the Rust maxminddb crate compiled to WebAssembly — the same tree walk a server-side reader performs, not a partial JavaScript reimplementation.
Loaded only when needed
The WebAssembly module is fetched the moment you first reach for the dropzone, so reading the page costs nothing extra and the tool is ready before your file is.
Use Cases
Debug a geolocation mismatch
A user says your site puts them in the wrong country. Open the exact database build you deploy and see the record your code is really reading.
Verify a build before shipping
Confirm the build date, database type and record count of a freshly downloaded file before it goes anywhere near production.
Inspect a custom database
Built your own MMDB with a writer library? The reader has no fixed schema, so it prints whatever fields you actually encoded.
Learn the MMDB format
Poke at a real database and watch how one record covers an entire network block — no CLI install, no language runtime, no account.
Related Network Tools
MMDB Reader FAQ
Drop the file onto the reader above. It opens in your browser using a WebAssembly build of the MaxMind DB library, shows the database metadata, and lets you query any IPv4 or IPv6 address. No install, no upload, no account.
No. The file is read with the browser File API and parsed inside a WebAssembly module on your own machine. Nothing about the database or the addresses you query is sent to nodedata.io.
MMDB is the MaxMind DB binary format, the format the IP intelligence industry standardised on. It packs a binary search tree over IP networks, a data section holding the records, and a metadata block into a single file, so a lookup is a handful of memory reads rather than a database query. Nearly every downloadable IP geolocation dataset ships in it.
Free datasets are usually country-accurate and roughly city-accurate, and are rebuilt weekly or monthly. Paid datasets add finer city resolution, confidence scores, and extra dimensions such as ISP, hosting domain, connection type and anonymous-network flags, with more frequent builds. Both ship as .mmdb files and both open in this reader.
Any valid MaxMind DB file, whoever produced it. City, country, ASN, ISP, domain, connection-type, anonymous-IP and combined enterprise datasets all work, as do databases you built yourself with a writer library.
Because the reader shows the raw record instead of forcing it into a City-shaped response. An ASN database returns autonomous system fields, an Anonymous IP database returns boolean flags, and your own database returns your own fields. Most online viewers hardcode the City schema and silently drop everything else.
MMDB files only store networks they have data for. Unallocated ranges, private addresses such as 192.168.0.0/16, and addresses outside the scope of that particular database simply have no record — that is a valid answer, not an error.
The database is held in memory, so the practical limit is your available RAM and the browser tab limit. Typical City databases of 60–90 MB open fine on a normal laptop; very large enterprise builds are better inspected with a native tool.
Once the page and the WebAssembly module have loaded, every lookup runs locally. You can go offline and keep querying the database that is already open.
IP data providers distribute city, country and ASN databases in MMDB format — some behind a free account, others with a paid subscription. Whichever one you use, the file opens here without leaving your browser.
Not here — this is a reader. Open-source writer libraries exist for Go, Perl and Python if you need to build or modify MMDB files yourself.
Yes. It is free, unlimited, and needs no account. If you would rather query IP intelligence over HTTP instead of shipping a database, see our API pricing.