Tool comparison
Image Converter vs JWT Decoder
Image Converter (conversion) and JWT Decoder (encoding) come from different categories but appear together in developer workflows. This guide explains what each does and when to reach for one over the other.
Bottom line
Image Converter handles image file format transformations; JWT Decoder parses authentication tokens. They belong to entirely separate problem domains — image processing vs API security debugging.
What each tool does
Image Converter
Image conversion is the process of re-encoding a digital image from one file format to another, changing the container, compression algorithm, and colour depth according to the target format's specification. Different image formats make different trade-offs: PNG uses lossless compression and supports full alpha transparency, making it ideal for screenshots, icons, and graphics with sharp edges. JPEG uses lossy compression optimised for photographs, achieving small file sizes at the cost of some detail. WebP is a modern format developed by Google that supports both lossless and lossy compression as well as alpha transparency — it is typically 25–35% smaller than JPEG or PNG at equivalent quality, and all modern browsers support it. AVIF (AV1 Image File Format) is the newest of the major formats, achieving roughly 50% smaller files than JPEG at equivalent visual quality at the cost of longer encoding times. TIFF is a lossless, uncompressed format used in print and photography workflows. GIF supports up to 256 colours and is primarily used for animations. This tool converts between PNG, JPEG, WebP, AVIF, TIFF, and GIF, and can rasterise SVG files to any of those formats. Conversion runs on the server using the Sharp library (libvips) — your image is sent over HTTPS and is not stored.
Open Image Converter →JWT Decoder
A JSON Web Token (JWT) is a compact, URL-safe string used to securely transmit claims between two parties. It consists of three base64url-encoded segments separated by dots: a header, a payload, and a signature. The header specifies the signing algorithm (such as HS256, RS256, or ES256). The payload contains claims — statements about an entity and additional metadata, such as a user ID (sub), an expiry time (exp), an issuer (iss), and any custom application-defined fields. The signature is computed over the header and payload using a secret or private key, allowing the recipient to verify that the token was issued by a trusted source and has not been modified. JWTs are the standard mechanism for stateless authentication in modern web applications: once issued, they travel with every API request (typically in the Authorization: Bearer header) and can be validated without a database lookup. This tool decodes the header and payload instantly without requiring a key, and can optionally verify the signature using your HMAC secret or RSA/ECDSA public key — all within your browser.
Open JWT Decoder →Side-by-side comparison
| Feature | Image Converter | JWT Decoder |
|---|---|---|
| Category | conversion | encoding |
| Primary purpose | Convert images between PNG, JPEG, WebP, AVIF, TIFF, GIF, and SVG formats | Decode and verify JSON Web Tokens — header, payload, claims, and signature. |
| Inputs | image, from, to, quality | token, secret, algorithm |
| Outputs | image, format, width, height, size_bytes | header, payload, signature, valid_structure, verified |
When to use each
Use Image Converter when…
How to convert PNG to WebP online
Reduce PNG file size by converting to WebP format for faster web page loading.
How to convert JPEG to AVIF online
Shrink photo file sizes dramatically by converting JPEG images to the AVIF format.
Use JWT Decoder when…
How to decode a JWT in your browser
Instantly inspect the header and payload of any JWT without installing software.
How to inspect an Auth0 JWT token
Read the claims inside an Auth0 access token or ID token to debug permissions and user data.
Frequently asked questions
- What is the maximum file size?
- 3 MB. This is set by the Vercel free tier request body limit. For larger images, use the API with a self-hosted instance — there is no size cap when self-hosted.
- Does conversion affect image quality?
- Lossless formats (PNG, TIFF) preserve every pixel exactly. Lossy formats (JPEG, WebP, AVIF) reduce file size by discarding perceptually insignificant detail. The quality slider controls this trade-off: 80 is a good default for web images, 90+ for print-quality exports, and 60–70 for thumbnails where small file size matters more than sharpness.
- Does this verify the signature?
- Yes — enter your HMAC secret or RSA/ECDSA public key in the Verify section. For HS* algorithms the secret is a plain text string; for RS*/ES* provide a PEM-formatted public key matching the private key that signed the token.
- Is my token sent to a server?
- The browser-side decoder never makes a network call — decoding is done entirely in JavaScript. The signature-verification call does send your token and key over HTTPS to a server-side endpoint, but neither is logged or stored.