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Base64 Encoder/Decoder & JWT Decoder

Encode, decode Base64 text, convert images to data URLs, and decode JWT tokens. All processing happens in your browser.

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Encode, Decode & Convert Base64 Data Online

A comprehensive toolkit for working with Base64 encoding. Encode text to Base64, decode Base64 strings back to text, convert images to data URLs for embedding in HTML/CSS, and decode JWT (JSON Web Token) payloads to inspect their claims and expiration dates.

Base64 encoding is essential for embedding binary data in text-based formats like JSON, XML, HTML, and email. Developers frequently need to encode API credentials, decode webhook payloads, convert small images to inline data URLs, or debug JWT tokens during authentication development.

All encoding and decoding runs entirely in your browser using native Web APIs. Your sensitive data — API keys, tokens, credentials — never leaves your device. Supports standard Base64 and URL-safe Base64 variants.

Frequently Asked Questions

What is Base64 encoding?
Base64 is a binary-to-text encoding scheme that represents binary data as an ASCII string. It is commonly used to embed images in HTML or CSS, transmit binary data over text-based protocols like email, and encode credentials in HTTP headers. The encoded output is roughly 33% larger than the original data.
What is URL-safe Base64?
Standard Base64 uses + and / characters that have special meaning in URLs and filenames. URL-safe Base64 replaces these with - and _ respectively, and removes trailing = padding. This variant is used in JWTs, data URIs in query strings, and anywhere a Base64 value needs to be part of a URL without additional percent-encoding.
What is a JWT token?
A JSON Web Token (JWT) is a compact, URL-safe means of representing claims between two parties. It consists of three Base64url-encoded parts separated by dots: a header (algorithm and type), a payload (the claims data), and a signature. JWTs are widely used for authentication and authorization in web applications, APIs, and single sign-on systems.
Is my data safe when using this tool?
Yes. All encoding, decoding, and JWT parsing happens entirely in your browser using JavaScript. No data is ever sent to a server. Your tokens and files remain private on your device. This is especially important for JWT tokens, which often contain sensitive user information.
Can this tool verify JWT signatures?
This tool decodes and displays the header, payload, and signature of a JWT, but it does not verify the signature. Signature verification requires the secret key (for HMAC algorithms) or the public key (for RSA/ECDSA), which should never be entered into a browser-based tool. For signature verification, use a server-side library.
What is the maximum file size for image conversion?
The image-to-data-URL converter supports files up to 10 MB. Keep in mind that Base64 encoding increases the size by approximately 33%, so a 10 MB image will produce a data URL of about 13.3 MB. For production use, data URLs are best suited for small images like icons and thumbnails.