Remove background from images with curl and the LassoCut API

Quickstart

Every request needs your key in the X-Api-Key header and exactly one image source. This example uses size=preview, which is covered by your account's 50 free previews a month (up to 10 a day).

curl -H "X-Api-Key: $LASSOCUT_API_KEY" \
     -F "image_file=@photo.jpg" \
     -F "size=preview" \
     -o no-bg.png \
     https://api.lassocut.com/v1.0/removebg

Tested against the production API on 27 September 2026 with this exact request; it returned a valid PNG.

Remove the background from a folder of images (bash)

This loop sends every JPG, PNG and WebP file in photos/ and writes out/<name>.png. It skips an image whose result already exists, so you can stop it and run it again: only the missing ones are sent, and paid.

mkdir -p out
for f in photos/*.jpg photos/*.jpeg photos/*.png photos/*.webp; do
  [ -e "$f" ] || continue                    # pattern matched no file
  name=$(basename "$f"); out="out/${name%.*}.png"
  if [ -e "$out" ]; then echo "skip $name"; continue; fi
  if curl -sS --fail-with-body --retry 4 \
       -H "X-Api-Key: $LASSOCUT_API_KEY" \
       -F "image_file=@$f" -F "size=full" -F "format=png" \
       -o "$out.part" https://api.lassocut.com/v1.0/removebg; then
    mv "$out.part" "$out"; echo "ok $name"
  else
    echo "failed $name: $(cat "$out.part" 2>/dev/null)" >&2; rm -f "$out.part"
  fi
done

• --fail-with-body (curl 7.76 or later) makes curl exit non-zero on an HTTP error while still saving the JSON error, which the loop prints.
• The result goes to a .part file first and is renamed only on success, so a failed call never leaves a file that the skip test would mistake for a finished one.
• --retry 4 retries 429 Rate limit exceeded and 503 answers and waits for the Retry-After header the API sends. curl prints a line for each retried attempt; the loop still prints ok once the image succeeds.
• format=png keeps transparency; PNG output is capped at 10 megapixels. For larger photos on a plain background, add -F "bg_color=ffffff", use format=jpg and give the output a .jpg name.

The loop sends one image at a time. For a few hundred images that is usually fine; for parallel calls from a shell, the LassoCut CLI does the same job with a --concurrency flag.

The same loop in PowerShell (Windows)

Windows 10 and 11 ship curl.exe. Call it by that full name: in Windows PowerShell 5.1, plain curl is an alias for Invoke-WebRequest, which takes different arguments.

New-Item -ItemType Directory -Force out | Out-Null
Get-ChildItem photos -File | Where-Object Extension -In '.jpg', '.jpeg', '.png', '.webp' | ForEach-Object {
  $out = Join-Path 'out' ($_.BaseName + '.png')
  if (Test-Path $out) { "skip $($_.Name)"; return }    # return = next file
  curl.exe -sS --fail-with-body --retry 4 `
    -H "X-Api-Key: $env:LASSOCUT_API_KEY" `
    -F "image_file=@$($_.FullName)" -F 'size=full' -F 'format=png' `
    -o "$out.part" https://api.lassocut.com/v1.0/removebg
  if ($LASTEXITCODE -eq 0) {
    Move-Item "$out.part" $out; "ok $($_.Name)"
  } else {
    Write-Warning "failed $($_.Name): $(Get-Content "$out.part" -Raw -ErrorAction SilentlyContinue)"
    Remove-Item "$out.part" -ErrorAction SilentlyContinue
  }
}

Set the key for the session first with $env:LASSOCUT_API_KEY = "your key". Both loops were run against a local test server that answers 429 with Retry-After before succeeding, to check the retry and skip behaviour.

Point an existing curl command at LassoCut

If you already call the remove.bg API with curl, two things change: the host and the key. Flags, form fields and the response format stay the same.

- curl -H "X-Api-Key: $REMOVE_BG_API_KEY" -F "image_file=@photo.jpg" -o no-bg.png https://api.remove.bg/v1.0/removebg
+ curl -H "X-Api-Key: $LASSOCUT_API_KEY" -F "image_file=@photo.jpg" -o no-bg.png https://api.lassocut.com/v1.0/removebg

For a full parameter-by-parameter comparison, see the migration guide.

Useful options

Full list, including framing, shadows and background images: API reference.

Marketplace preset and shadow

A marketplace preset frames the cut-out on the canvas, white background and file size that marketplace expects, and shadow_type=cast adds a cast shadow. The response header X-Compliance says whether the result meets the rules LassoCut checks. With a preset, crop, crop_margin, scale and position are ignored. See marketplace presets.

curl --fail-with-body -H "X-Api-Key: $LASSOCUT_API_KEY" \
     -F "image_file=@product.jpg" \
     -F "preset=amazon" \
     -F "shadow_type=cast" -F "shadow_angle=45" \
     -D headers.txt -o amazon.jpg \
     https://api.lassocut.com/v1.0/removebg
grep -i x-compliance headers.txt

Common errors

Errors return JSON: {"errors": [{"code": "…", "title": "…"}]}. Nothing is charged on an error.

Full list: API reference.

Next steps

Read the full API reference for every parameter and header, or the migration guide if you're moving a script that already calls remove.bg. No key yet? Create a free account, or try LassoCut on your image first, no key required.