Base64 Encoder & Decoder
Encode and decode strings using Base64, URL encoding, HTML entities, or ROT13. Results update as you type.
About the String Encoder & Decoder
This tool provides four common string encoding and decoding methods in one place. All processing happens entirely in your browser, so your data is never sent to any server.
Base64 Encoding
Base64 encodes binary data into ASCII text using a 64-character alphabet. It is commonly used for embedding images in CSS or HTML, transmitting data in URLs or JSON, encoding email attachments (MIME), and storing binary data as text in databases.
URL Encoding (Percent Encoding)
URL encoding replaces special characters with percent-encoded equivalents (like %20 for a space). This is essential for including special characters in URLs, query parameters, and form submissions. Use this when building URLs programmatically or debugging encoded URLs.
HTML Entity Encoding
HTML entity encoding converts special HTML characters like <, >, &, and quotes into their entity equivalents. This prevents cross-site scripting (XSS) vulnerabilities and ensures special characters display correctly in HTML pages.
ROT13 Cipher
ROT13 is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. It is its own inverse: applying ROT13 twice returns the original text. ROT13 is commonly used for obscuring spoilers, punchlines, and puzzle answers online. It is not encryption and provides no security.
When to Use Each Encoding
- Base64 — Embedding binary data in text formats, data URIs, API tokens
- URL encoding — Building safe URLs, query strings, form data
- HTML entities — Sanitizing user input for HTML display, escaping special characters
- ROT13 — Hiding spoilers, casual text obfuscation (not security)