Image to Base64

Convert one or more images to base64-encoded strings and data URIs. Supports optional format conversion, quality control, and resizing. Useful for embedding images directly in HTML, CSS, JSON, or email templates.

API Endpoint

POST /api/v1/tools/image-to-base64

Accepts multipart form data with one or more image files and an optional JSON settings field.

Parameters

Parameter	Type	Required	Default	Description
outputFormat	string	No	"original"	Convert before encoding: original, jpeg, png, webp, avif, jxl
quality	number	No	80	Output quality for lossy formats (1 to 100)
maxWidth	number	No	0	Maximum width in pixels (0 = no resize, will not enlarge)
maxHeight	number	No	0	Maximum height in pixels (0 = no resize, will not enlarge)

Example Request

curl -X POST http://localhost:1349/api/v1/tools/image-to-base64 \
  -H "Authorization: Bearer si_your-api-key" \
  -F "[email protected]" \
  -F 'settings={"outputFormat": "webp", "quality": 80, "maxWidth": 200}'

Multiple files:

curl -X POST http://localhost:1349/api/v1/tools/image-to-base64 \
  -H "Authorization: Bearer si_your-api-key" \
  -F "[email protected]" \
  -F "[email protected]" \
  -F "[email protected]" \
  -F 'settings={"outputFormat": "original"}'

Example Response

{
  "results": [
    {
      "filename": "icon.png",
      "mimeType": "image/webp",
      "width": 200,
      "height": 200,
      "originalSize": 45000,
      "encodedSize": 28800,
      "overheadPercent": -36.0,
      "base64": "UklGRlYAAABXRUJQ...",
      "dataUri": "data:image/webp;base64,UklGRlYAAABXRUJQ..."
    }
  ],
  "errors": []
}

Response Fields

Field	Type	Description
results	array	Successfully converted images
errors	array	Images that failed to process (with filename and error message)

Result Object

Field	Type	Description
filename	string	Original filename
mimeType	string	MIME type of the encoded output
width	number	Final width in pixels (after any resizing)
height	number	Final height in pixels (after any resizing)
originalSize	number	Original file size in bytes
encodedSize	number	Size of the base64 string in bytes
overheadPercent	number	Percentage size difference vs original (positive = larger, negative = smaller)
base64	string	Raw base64-encoded image data
dataUri	string	Complete data URI ready for use in src attributes

Notes

• Base64 encoding typically increases size by approximately 33% compared to the binary file. The overheadPercent field shows the actual difference.
• When outputFormat is "original", HEIC/HEIF files are converted to JPEG (since browsers cannot display HEIC in data URIs).
• The maxWidth and maxHeight options resize using fit: inside with withoutEnlargement, so images smaller than the specified dimensions are not upscaled.
• Multiple files can be processed in a single request. Each file is processed independently, and failures do not prevent other files from succeeding.
• SVG files are passed through as image/svg+xml without re-encoding (unless a format conversion is requested).
• This is a read-only endpoint. It does not produce a downloadable file or a jobId. The base64 data is returned directly in the response body.