what is mongodb gridfs?

GridFS stands for Grid File System. MongoDB GridFS is a specification for storing and retrieving large files (such as images, videos, audio files, or any binary data) in MongoDB that exceed the BSON document size limit of 16 MB.

How It Works

GridFS uses two collections to manage files:

1. fs.files – Stores file metadata such as filename, upload date, size, and a unique ID.
2. fs.chunks – Stores the actual file data in chunks, each linked to the parent file via an ObjectId.

Each chunk document in fs.chunks looks like this:

{
  "_id": ObjectId("..."),
  "files_id": ObjectId("..."),  // reference to fs.files._id
  "n": 0,                       // chunk sequence number
  "data": BinData(...)           // binary data
}

Example Flow

1. You upload a large file.
2. GridFS splits it into chunks (e.g., 255 KB each).
3. Each chunk is stored in fs.chunks.
4. Metadata about the file (like name, length, and MD5 hash) goes into fs.files.
5. When you download or read the file, GridFS reassembles it in order.

Tools & Drivers

Most MongoDB drivers include built-in support for GridFS.
For example:

• Node.js: GridFSBucket API in the official mongodb driver.
• Python: gridfs module in pymongo.
• Mongo Shell: Some tools like mongofiles let you work with GridFS directly.

How to Add (Upload) Images to GridFS Manually via Command Line

MongoDB provides a built-in tool called mongofiles for working with GridFS from the terminal.

You can use it to upload, list, download, or delete files in GridFS — no programming needed.

Step-by-Step Example

1. Make sure MongoDB is running

If you’re running MongoDB locally:

mongod

2. Open another terminal window

3. Use the mongofiles tool

Here’s the syntax:

mongofiles --db <database_name> put <filename>

Example — Upload an Image

Suppose you have a file named photo.jpg in your current folder.

Run this command:

mongofiles --db=mydatabase put photo.jpg

Explanation:

• --db=mydatabase → stores file in the mydatabase database
• put photo.jpg → uploads the file into GridFS

After Uploading

If you open the MongoDB shell and connect to your database:

mongosh
use mydatabase

Then check the collections:

show collections

You’ll see:

fs.files
fs.chunks

Now, you can inspect what’s inside:

db.fs.files.find().pretty()

You’ll get something like:

{
  "_id": ObjectId("654240f57b7d9e47f1fce9b2"),
  "length": 523424,
  "chunkSize": 261120,
  "uploadDate": ISODate("2025-11-01T12:00:00Z"),
  "filename": "photo.jpg"
}

And in fs.chunks:

db.fs.chunks.find().limit(2).pretty()

Each document looks like:

{
  "_id": ObjectId("654240f57b7d9e47f1fce9b3"),
  "files_id": ObjectId("654240f57b7d9e47f1fce9b2"),
  "n": 0,
  "data": BinData(0,"/9j/4AAQSkZJRgABAQ...")
}

To Download the Image Back

If you want to download the file again from GridFS:

mongofiles --db=mydatabase get photo.jpg

This will create a new file named photo.jpg in your current folder.

To Delete the Image

mongofiles --db=mydatabase delete photo.jpg

Full Example Workflow

Step 1 — Start MongoDB

mongod --dbpath "C:\data\db"

Step 2 — Upload a file

mongofiles --db=test put 1.png

Step 3 — List files in GridFS

mongofiles --db=test list

Step 4 — Download the file

mongofiles --db=test get 1.png

Step 5 — Delete it (optional)

mongofiles --db=test delete 1.png