How do you handle file uploads in Postman?

Answer

File Upload in Postman

Postman supports file uploads using the form-data body type, which sends files as multipart/form-data.

Step-by-Step File Upload

✓Set method to POST (or PUT)
✓Enter the upload URL: https://api.example.com/upload
✓Click the Body tab
✓Select form-data radio button
✓
Add a key field:
- ✓Type: file (name of the file parameter the API expects)
- ✓Hover over the key field → dropdown appears
- ✓Change type from Text to File
✓Click "Select Files" in the Value column
✓Browse and select your file (PDF, image, CSV, etc.)
✓Click Send

Multiple Files

CODE

KEY         TYPE    VALUE
files       File    [Select document1.pdf]
files       File    [Select document2.pdf]
description Text    "Batch upload test"

File Upload with Additional Fields

CODE

KEY             TYPE    VALUE
file            File    [Select profile.jpg]
user_id         Text    12345
title           Text    "Profile Picture"
is_public       Text    true

Checking Upload Worked

JavaScript

// In Tests tab — validate upload response
pm.test("File uploaded successfully", function () {
    pm.response.to.have.status(200);
    const json = pm.response.json();
    pm.expect(json.file_id).to.be.a('string');
    pm.expect(json.url).to.match(/^https/);
    pm.expect(json.size).to.be.above(0);
});

pm.test("Filename is correct", function () {
    const json = pm.response.json();
    pm.expect(json.filename).to.include("profile");
});

Using Variables for File Paths

In Postman Desktop, you can use the pm.iterationData to pass file paths in Collection Runner:

JavaScript

// Pre-request Script
const filePath = pm.iterationData.get("file_path");
// Note: Postman doesn't support dynamic file paths via variables
// File selection must be done manually in form-data

Common Errors

Error	Cause	Fix
400 Bad Request	Wrong field name	Match API's expected parameter name
413 Payload Too Large	File too big	Check API's max file size
415 Unsupported Media Type	Wrong content type	Use form-data, not raw
File not attached	Type is Text not File	Change key type to File

Testing Upload Limits

Test with:

✓✅ Valid file types (PDF, JPG, PNG, CSV)
✓✅ File at size limit (e.g., exactly 5MB)
✓❌ Oversized file (e.g., 6MB when limit is 5MB) → expect 413
✓❌ Invalid file type (e.g., .exe when only images allowed) → expect 400