Skip to content
pdfconversionapi

QOI to WebP API

POST a QOI to /v2/convert/qoi/to/webp and get a lossless WebP that browsers can show. Every pixel and alpha value is kept, and the sample card came out at 63% of the QOI's size.

Endpoint
POST /v2/convert/qoi/to/webp
Accepts
qoi
Sample timing
1 ms median of 5 runsHow we measure
Request size
Up to 10 MB on the Free plan or 100 MB on paid plans, all files together

Request and response

Every sample below ran against the API before this page was published. Set PDFCONVERSIONAPI_KEY to your key and run it as is.

curl -sS -X POST \
  https://api.pdfconversionapi.com/v2/convert/qoi/to/webp \
  -H "Authorization: Bearer $PDFCONVERSIONAPI_KEY" \
  -F File=@trail-map-card.qoi \
  -o response.json

# FileData is base64. Save the first file in converted/,
# or print the JSON error.
if jq -e '.Files' response.json > /dev/null; then
  mkdir -p converted
  name=$(jq -r '.Files[0].FileName' response.json)
  jq -r '.Files[0].FileData' response.json \
    | base64 --decode > "converted/$name"
else
  cat response.json
fi
200 OK1 ms median1 file, 42 KB
{
  "ConversionCost": 1,
  "ConversionTime": 0.001,
  "Files": [
    {
      "FileName": "trail-map-card.webp",
      "FileExt": "webp",
      "FileSize": 42524,
      "FileData": "UklGRhSmAABXRUJQVlA4TAim…"
    }
  ]
}

Response from our test run on 2026-11-03. ConversionTime shows the median of 5 runs. FileData is shortened here; the real response carries the whole file as base64.

The sample, converted

The same file the code sends. Download the input and the output and compare them yourself.

First page of trail-map-card.webp, rendered by the API
Input
trail-map-card.qoi (66 KB)
Output
trail-map-card.webp (42 KB)
Source
A 400 x 300 trail map card with a sunrise sky, rounded transparent corners and a soft drop shadow, drawn by us and saved as a 4-channel QOI. (CC0-1.0). How it was made
Made by
2026-11-04, API build 9eeeb0640aba

Parameters

Send these as form fields next to the file. Names are case-insensitive. If you set one of the documented options below that we don't support yet, the request fails with a 400 that names it instead of returning a file made without it.

ParameterWhat it does
ImageWidthintegerOutput width, height to match: 128 gives a 128 × 96 WebP of 11,552 bytes.Values: 1–16384 for WebP
ImageHeightintegerOutput height; with a width too, the picture fits both.Values: 1–16384
ScaleProportionsboolean, default truefalse stretches to the exact width × height pair.
ScaleIfLargerboolean, default falsetrue never enlarges a QOI that is already small enough.
ScaleImageboolean, default truefalse crops a top-left window (2,170 bytes for 200 × 100).
ColorSpaceenum, default defaultgray cut the card to 18,576 bytes and monochrome to 3,768, with alpha still in place.Values: default, rgb, gray, monochrome; cmyk returns 400
TransparentColorstringOne exact color to make transparent before encoding.Values: #RRGGBB, R,G,B or a basic color name
FileNamestringFile name for the WebP, without extension.
StoreFileboolean, default falsetrue returns a URL that works for 3 hours.

What carries over, and what doesn't

Kept

  • Every pixel, including the 17,245 semi-transparent ones in the card's shadow and anti-aliased corners
  • 400 × 300, with no resampling unless you ask
  • Opaque pictures without an added alpha channel: a 3-channel QOI, or a 4-channel one with no transparent pixel, becomes an RGB WebP (38,144 bytes for a 3-channel copy of the card)

Lost or not yet supported

  • Nothing in the picture. The QOI colorspace byte has no WebP equivalent and is dropped.
  • Any chance of a lossy WebP: ImageQuality is ignored on this route.
  • Very large dimensions. WebP's ceiling is 16,384 px per side, far below what a QOI header can state.

Limits

  • One QOI per request.
  • 16,384 px per side for WebP: a 16,385 × 2 QOI returned 413 WebP images can be at most 16,384 pixels on a side, and this one is 16,385×2. If you sent ImageWidth or ImageHeight, it adds ; lower ImageWidth or ImageHeight.
  • 100,000,000 pixels per image (413 above, checked from the header).
  • Requests up to 10 MB on the Free plan or 100 MB on paid plans; 120 seconds per conversion.

Where teams use it

Putting QOI art on a web page

Engines and tools that save QOI produce files browsers can't render. Lossless WebP keeps the pixels exact, alpha included, and current versions of the major browsers display it.

Smaller lossless archives

QOI keeps its encoding simple rather than small. If you keep frames or screenshots long term, lossless WebP stores the same pixels in fewer bytes: 63% of the QOI for the sample.

Questions

Is the WebP really lossless?

Yes. It is always written in WebP's lossless mode, and decoding the sample gives back all 120,000 RGBA values of the QOI unchanged.

How do the sizes compare?

For the trail map card: 67,304 bytes as QOI, 49,290 as PNG and 42,524 as lossless WebP. Results vary with the image, so measure on your own files.

Why did my 20,000 px wide QOI fail?

WebP cannot store more than 16,384 px per side, so the API answers 413 with that limit and the image's size. Send ImageWidth=16384 or less to scale it down in the same request, or choose PNG, which has no such limit.

Convert your first QOI file in a minute.