mongoexport - Get Your MongoDB Data Out

mongoexport is MongoDB's tool for getting data out of collections in JSON or CSV format. Version 100.13.0 is current as of August 2025. It's decent for pulling data when you need it readable, but it's slow as hell on big collections and has some gotchas that'll bite you.

The truth is, mongoexport fills a specific niche - when you need human-readable data exports from MongoDB. But like a lot of MongoDB tooling, it works great until it doesn't, and then you're stuck debugging memory issues and performance problems that make you question your database choices.

What It Actually Does Well

JSON Export: Keeps your document structure intact with nested objects and arrays. Works fine for smaller collections when you need readable data for other applications or APIs that consume JSON format.

CSV Export: Flattens everything into spreadsheet format. Good luck if you have nested data - it turns into useless strings. But if you need to get data into Excel for some PM who insists on pivot tables, it works.

Query Filtering: You can use MongoDB query syntax with --query to export subsets. This actually saves your ass when you don't want to dump 50 million records just to get last week's data. The query operators work exactly like normal MongoDB finds.

Authentication: Supports the usual MongoDB auth methods including Atlas connections. At least it doesn't make you jump through hoops to connect securely via SSL/TLS.

When mongoexport Will Ruin Your Day

Large Collections: mongoexport will eat your RAM and crawl like a dying turtle on big datasets. We're talking 18 fucking hours for what should take 30 minutes. I've watched it choke and die on collections over 10 million docs while the server sits there with 15 idle CPU cores. This Stack Overflow thread is full of engineers losing their minds over 0.1% progress after 6 hours.

Memory Usage: It loads way more shit into memory than it should. Seriously, don't run this on a production box with limited RAM or you'll get this beauty: mongoexport: killed (signal 9) when the OOM killer decides your export isn't worth keeping alive. Understanding memory management becomes critical for large exports.

NOT for Backups: MongoDB screams this at you in the docs - don't use mongoexport for backups. It loses BSON type information. Use mongodump or your backup will be garbage when you try to restore it.

CSV Structure Issues: Nested objects become stringified JSON blobs in CSV. Arrays get flattened into comma-separated strings inside quoted fields. It's a mess if you have complex documents.

The bottom line: mongoexport is fine for quick data pulls and analysis on smaller datasets, but if you're working with production-scale collections or need reliable backups, you'll want to explore other options. Which brings us to how it stacks up against the competition...

Getting It Installed (When It Actually Works)

mongoexport comes with the MongoDB Database Tools package, which is separate from the MongoDB server. This drives me nuts because older MongoDB versions used to include the tools.

Installation Methods (And Their Problems):

Package Managers: apt-get install mongodb-database-tools works sometimes. Half the time you get this shit:

E: Unable to locate package mongodb-database-tools

Or it installs version 4.2 from 2019 like some kind of joke. On macOS, brew install mongodb/brew/mongodb-database-tools actually works but takes 20 minutes to compile dependencies you don't need.

Direct Download: Download the pre-compiled binaries and drop them in your PATH environment variable. This is actually the safest bet, but you'll probably hit missing dependency hell on some Linux distros. Check the system requirements first.

Docker: Available in MongoDB's official Docker images, but debugging connection issues when everything's containerized is a pain in the ass.

Commands That Actually Work

Basic Export (When Collection Isn't Huge):

mongoexport --collection=events --db=reporting --out=events.json

This uses all the default connection options to localhost:27017.

CSV Export with Specific Fields (CSV Flattening Will Ruin Complex Data):

mongoexport --db=users --collection=contacts --type=csv --fields=name,email,created_at --out=contacts.csv

The --fields option is required for CSV format. See the CSV formatting documentation for more pain.

Filtered Export (Actually Useful):

mongoexport --db=sales --collection=orders --query='{"status": "completed", "created": {"$gte": {"$date": "2025-01-01T00:00:00Z"}}}' --out=completed_orders.json

Production Reality (Where Everything Goes Wrong)

Memory Will Kill You: mongoexport loads way more data into memory than it should. I've watched it crash with Killed (signal 9) on a 16GB server trying to export a collection that's only 2GB on disk. You'll see this in dmesg:

Out of memory: Kill process 15234 (mongoexport) score 901 or sacrifice child
Killed process 15234 (mongoexport) total-vm:12435788kB, anon-rss:11234567kB

The MongoDB forums are basically just people posting "why did mongoexport eat 24GB of RAM and crash?"

Pagination Is Your Only Hope: For big collections, chunk it with --skip and --limit. Sucks to script, but beats crashing:

## Export in 100k chunks - prepare to babysit this
mongoexport --skip=0 --limit=100000 --db=big --collection=data --out=data_1.json
mongoexport --skip=100000 --limit=100000 --db=big --collection=data --out=data_2.json

Connection Timeouts on Sharded Clusters: If you're hitting a sharded cluster, expect random connection drops on large exports. Use `--readPreference=secondary` to avoid hitting the primary, but prepare for this lovely error anyway:

2025-09-01T14:32:15.342+0000 E QUERY    [js] Error: error doing query: failed: 
network error while attempting to run command 'getMore' on host 'mongo-shard-02:27018'

Authentication Headaches: Put your credentials in a config file unless you want your MongoDB password in your shell history. Use --config=/path/to/config.yaml and lock down the file permissions properly.

After dealing with these installation and production headaches, you'll probably have questions. Trust me, everyone does. Here are the answers to the questions you'll inevitably ask after your first mongoexport disaster...