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PNG to WebP API#

The PNG to WebP API converts a PNG image to WebP format with a single request to POST /v1/convert/png-to-webp. Upload a .png file as multipart/form-data and receive raw WebP bytes back, or set direct_download=false to get JSON metadata with a presigned download URL. Transparency (alpha channel) is preserved in the WebP output.

Endpoint#

POST /v1/convert/png-to-webp

Content-Type: multipart/form-data

Accepted input: .png files

Output format: .webp (image/webp)

Authentication#

Requires either a private API key or a JWT token from a public key.

X-API-Key: sk_your_private_key

Or:

Authorization: Bearer <jwt_token>

Request Parameters#

Parameter	Type	Required	Default	Description
`file`	file	Yes	--	The `.png` image file to convert.
`output_filename`	`string`	No	Input filename	Custom output filename. The `.webp` extension is added automatically.
`direct_download`	`boolean`	No	`true`	When `true`, returns raw image bytes. When `false`, returns JSON metadata with a presigned download URL.

Conversion Details#

Uses Pillow for direct format conversion
If the PNG has an alpha channel (RGBA), it is preserved in the WebP output
Non-RGBA/RGB modes are converted to RGBA
Output quality is set to maximum (100)
WebP supports both lossy and lossless compression; this conversion uses quality 100 for near-lossless output

Response#

Direct Download (`direct_download=true`, default)#

HTTP 200 OK
Content-Type: image/webp
Content-Disposition: inline; filename="image_20260405_123456789.webp"

Returns raw image bytes.

Metadata Response (`direct_download=false`)#

{
    "presigned_url": "https://spaces.example.com/...",
    "object_key": "env/files/{project_id}/png-to-webp/image_20260405_123456789.webp",
    "filename": "image_20260405_123456789.webp",
    "file_size": 45678,
    "conversion_time_seconds": 0.5
}

Code Examples#

Python#

import requests

with open("image.png", "rb") as f:
    response = requests.post(
        "https://api.enconvert.com/v1/convert/png-to-webp",
        headers={"X-API-Key": "sk_your_private_key"},
        files={"file": ("image.png", f)}
    )

with open("image_20260405_123456789.webp", "wb") as out:
    out.write(response.content)

Node.js#

const form = new FormData();
form.append("file", fs.createReadStream("image.png"));

const response = await fetch("https://api.enconvert.com/v1/convert/png-to-webp", {
    method: "POST",
    headers: { "X-API-Key": "sk_your_private_key" },
    body: form
});

fs.writeFileSync("image_20260405_123456789.webp", Buffer.from(await response.arrayBuffer()));

PHP#

$ch = curl_init("https://api.enconvert.com/v1/convert/png-to-webp");
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ["X-API-Key: sk_your_private_key"],
    CURLOPT_POSTFIELDS => ["file" => new CURLFile("image.png")]
]);
$output = curl_exec($ch);
curl_close($ch);
file_put_contents("image_20260405_123456789.webp", $output);

Go#

body := &bytes.Buffer{}
writer := multipart.NewWriter(body)
part, _ := writer.CreateFormFile("file", "image.png")
file, _ := os.Open("image.png")
io.Copy(part, file)
writer.Close()

req, _ := http.NewRequest("POST", "https://api.enconvert.com/v1/convert/png-to-webp", body)
req.Header.Set("Content-Type", writer.FormDataContentType())
req.Header.Set("X-API-Key", "sk_your_private_key")
resp, _ := http.DefaultClient.Do(req)

Error Responses#

Status	Condition
`400 Bad Request`	File is not a `.png` file
`400 Bad Request`	Image conversion failed (corrupt or unsupported file)
`401 Unauthorized`	Missing or invalid API key / JWT token
`402 Payment Required`	Monthly ops allowance exhausted
`402 Payment Required`	Storage limit reached
`413 Payload Too Large`	File exceeds plan's maximum file size

Limits#

Limit	Value
Max file size	Plan-dependent (Founding: 5 MB)
Output quality	Maximum (not configurable)
Monthly conversions	Plan-dependent

Frequently asked questions#

How do I convert PNG to WebP with a REST API?#

Send a POST request to /v1/convert/png-to-webp with your .png file in a multipart/form-data body, authenticated via X-API-Key or a JWT Authorization: Bearer token. The converted WebP is returned as raw image bytes by default.

Is PNG transparency preserved when converting to WebP?#

Yes. If the PNG has an alpha channel (RGBA), it is preserved in the WebP output; non-RGBA/RGB modes are converted to RGBA first.

Is the WebP output lossy or lossless?#

WebP supports both lossy and lossless compression; this conversion uses quality 100 for near-lossless output. The quality setting is not configurable.

Can I get a download URL instead of raw WebP bytes?#

Yes. Set direct_download=false and the API returns JSON metadata with a presigned_url, filename, file_size, and conversion_time_seconds.

What is the maximum PNG file size I can upload?#

Max file size is plan-dependent (5 MB on the Founding plan). Larger files are rejected with 413 Payload Too Large.

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API Documentation