EVMTools

Base64 Encoder / Decoder

Encode and decode Base64 strings online. Supports text and hex input with URL-safe Base64 option for Ethereum development.

Input format:

Examples

About Base64 Encoding

  • Base64 encodes binary data into ASCII text using 64 characters (A-Z, a-z, 0-9, +, /)
  • URL-safe variant replaces + with - and / with _ (RFC 4648)
  • Common uses: encoding ABI data, JWT tokens, data URIs, API payloads
  • Encoded output is ~33% larger than the original binary data

How to Use This Base64 Encoder / Decoder

This free online Base64 tool lets you encode and decode data in both standard and URL-safe Base64 formats. It supports text and hex input modes for maximum flexibility.

  1. Select your input mode — choose between text (UTF-8) or hex input depending on your data format.
  2. Enter or paste your data into the input field. For hex input, you can include or omit the 0x prefix.
  3. Click Encode to convert your input to Base64, or click Decode to convert Base64 back to its original form.
  4. Toggle URL-safe mode if you need Base64 output that is safe for URLs and filenames.
  5. Copy the result for use in your code, APIs, or on-chain metadata.

All encoding and decoding happens locally in your browser. No data leaves your machine.

Common Use Cases

  • On-chain NFT metadata — Encode JSON metadata and SVG images as Base64 data URIs for fully on-chain NFTs.
  • JWT token inspection — Decode Base64 segments of JWT tokens to inspect claims and payloads.
  • API data encoding — Encode binary data or complex objects for safe transmission in HTTP headers, query parameters, or JSON payloads.
  • Smart contract bytecode — Convert between hex bytecode and Base64 for storage or display in different contexts.
  • Data URI creation — Generate data URIs for embedding images, fonts, or other assets directly in HTML or contract metadata.

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Frequently Asked Questions

What is Base64 encoding?

Base64 is a binary-to-text encoding scheme that represents binary data using 64 ASCII characters (A-Z, a-z, 0-9, +, /). It converts every 3 bytes of input into 4 ASCII characters, making binary data safe for transmission through text-based protocols like HTTP, email, and JSON. The output is approximately 33% larger than the input.

What is URL-safe Base64?

URL-safe Base64 replaces the + and / characters with - and _ respectively, and typically omits the = padding. This variant is safe for use in URLs and filenames without percent-encoding. It is commonly used in JWTs (JSON Web Tokens), data URIs, and API parameters where standard Base64 characters would cause issues.

How is Base64 used in NFTs and on-chain data?

On-chain NFTs use Base64 to encode metadata and SVG images directly in the token URI. The tokenURI returns a data URI like 'data:application/json;base64,...' containing the Base64-encoded JSON metadata, which itself may contain Base64-encoded SVG or image data. This enables fully on-chain NFTs without external storage.

What is the difference between Base64 and hex encoding?

Base64 uses 64 characters and is more space-efficient, producing output that is 33% larger than the input. Hex encoding uses only 16 characters (0-9, A-F) and doubles the size of the input. Ethereum primarily uses hex encoding for addresses, hashes, and calldata, while Base64 is more common for metadata, images, and web APIs.

Can I encode binary files with Base64?

Yes. Base64 can encode any binary data including images, PDFs, and compiled bytecode. However, be aware that Base64 increases the data size by approximately 33%. For on-chain storage, this overhead translates directly to higher gas costs, so it is important to minimize data before Base64 encoding.

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