Developer API

A REST API for server-side image compression — for automation, backends, and pipelines. This is a separate product from the free browser tool above: requests here are processed on our servers (in memory, never persisted to disk), gated by an API key tied to your plan. Get a key from the dashboard.

Authentication

Pass your API key as a bearer token on every request:

Authorization: Bearer webpninja_live_<your_key>

Compress an image

POST /api/v1/compress — multipart form upload. Returns the compressed image bytes with the matching Content-Type.

Field	Description
file	The image to compress (multipart file field). Any format sharp can decode.
format	Output format: `webp`, `jpeg`, `png`, or `avif`.
quality	10–100, default 80. Same compression settings as the browser tool at the same quality.

curl -X POST https://api.webpninja.com/api/v1/compress \
  -H "Authorization: Bearer webpninja_live_your_key" \
  -F "file=@photo.png" \
  -F "format=webp" \
  -F "quality=75" \
  --output photo.webp

Quotas & rate limits

Each plan includes a monthly compression quota that resets at the start of your billing period. Exceeding it returns 429 Too Many Requests. See current plan quotas and your usage on the dashboard.

Errors

Status	Meaning
400	Missing file, or an invalid format/quality value.
401	Missing, invalid, or revoked API key.
422	The file couldn't be decoded or compressed.
429	Monthly quota exceeded for your plan.