Overview

Filestack is a file handling API that lets you upload, transform, and deliver files from any source — local disk, URL, cloud storage, or social network. It handles multipart uploads, CDN delivery, and on-the-fly image transformations server-side, so you do not need to build your own upload infrastructure. It is widely used in SaaS products where users need to attach documents, images, or videos.

💡

Beginner Tip

You need a free Filestack API key to upload files. Start by uploading a single file via the REST endpoint using a multipart POST, then inspect the returned handle to construct a delivery URL.

Available Data

Filestack data via REST API
JSON-formatted response data
Requires API key authentication

Example Response

JSON Response
{
  "file_id": "f_abc123",
  "filename": "document.pdf",
  "size_bytes": 1048576,
  "mime_type": "application/pdf",
  "download_url": "https://example.com/files/f_abc123",
  "created_at": "2025-01-15T10:00:00Z"
}

Field Reference

url Full CDN URL where the uploaded file can be accessed publicly
handle Unique identifier for the file used to construct transform and delivery URLs
filename Original name of the file that was uploaded
size File size in bytes
type MIME type of the uploaded file, e.g. image/jpeg or application/pdf
mimetype Duplicate MIME type field returned for compatibility with older SDK versions

Implementation Example

const url = "https://www.filestack.com/";
// Replace headers or query params with the values required by this API.
const response = await fetch(url, {
  headers: {
  "X-API-Key": "YOUR_API_KEY"
  }
});
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

What Can You Build?

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

Common Errors & Troubleshooting

401 Unauthorized Missing or invalid API key in the request
Include your Filestack API key as a query parameter: ?key=YOUR_API_KEY
File size limit exceeded Free tier restricts uploads to 10 MB per file
Check your plan limits in the Filestack dashboard and either compress the file or upgrade your account
400 Bad Request on transform URL Incorrect transformation parameter syntax in the CDN URL
Chain transformations correctly in the path, e.g. /resize=width:200/output=format:webp/YOUR_HANDLE

Matrix Score Breakdown

🌐 Reachability 30/30
⚡ Speed 5/20
🔒 Security 15/15
🛠 Developer XP 12/20
✓ Reliability 10/15

Partially tested on Apr 5, 2026

Technical Specifications

Auth API Key
HTTPS REQUIRED
CORS UNKNOWN
Difficulty Intermediate
Verified: 2026-04-04

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