Image Optimization API reference

Base URL: https://api.justapi.tech (alias: https://img.justapi.tech)

options for POST /v1/image/optimize

"options": {
  "width": 1600, "height": null, "fit": "inside",  // inside | cover | contain | fill
  "format": "jpeg",            // jpeg | webp | avif | png | auto
  "quality": 76,
  "mozjpeg": true,
  "progressive": false,        // must be false if the output is embedded in a PDF
  "chroma_subsampling": "4:2:0",
  "strip_metadata": true,
  "auto_orient": true,         // applies EXIF rotation, THEN strips it
  "max_bytes": 250000,         // binary quality search until the output is under this
  "keep_source": false         // default: the original is deleted after processing
}

Two defaults exist specifically because getting them wrong is a common, hard-to-debug failure:

progressive: false. Progressive JPEG is not valid inside DCTDecode streams. Most PDF viewers render it wrong or blank. If the destination is a PDF, always baseline.

auto_orient: true. Phone photos carry orientation in EXIF, not in the pixel data. Stripping EXIF before rotating leaves every landscape photo sideways. We rotate first, then strip.

POST /v1/image/batch

Same options object applied to every image, plus an optional per_image_options keyed by ref for per-file overrides. Up to 250 images (25 on the free tier). Individual failures do not fail the batch — each result comes back tagged ok or failed against its own ref.

GET /v1/image/t/{key_id}/{transform}/{file_id}

URL-based transform, drop-in compatible with the Bytescale query-param pattern:

https://img.justapi.tech/t/k_7f3a/w_1200,q_76,f_jpg/fil_01JBX...

Transforms: w_ width, h_ height, q_ quality, f_ format, fit_, g_ gravity, bl_ blur, sh_ sharpen, r_ rotate. Cached at Cloudflare's edge — a repeated request for the same transform is a cache hit and is not billed again.

Example

curl https://api.justapi.tech/v1/image/optimize \
  -H "Authorization: Bearer ak_live_..." \
  -H "Content-Type: application/json" \
  -d '{"source":{"url":"https://example.com/photo.jpg"},"options":{"width":1600,"max_bytes":250000}}'

Full envelope, error catalog and billing rule are the same across every JustAPI service — see the API reference index and error codes.