Base64 text / file
{{ inputBytes }} bytes in • {{ outputBytes }} bytes out (×{{ sizeRatio }})
Decoded text
Recent Decodes
  • {{ h }}
Categories: Base64 , Decoder , Text
Export to PDF Fullscreen

The Base64 encoding converts binary data into ASCII text using a 64-character alphabet. The alphabet comprises uppercase letters, lowercase letters, digits, plus sign, and slash. Each four encoded characters represent three bytes of original data. This scheme protects data integrity when transferring through channels that favour textual content.

You use the Base64 Decoder to reverse this encoding process efficiently inside your browser. The tool reads the encoded string or file, applies the algorithm, and reproduces the original content. It supports the URL-safe variant and automatically repairs missing padding. Drag-and-drop input and clipboard integration streamline your workflow.

Decoding locally avoids uploading confidential data to remote servers. Developers quickly inspect API payloads. Sysadmins recover configuration secrets stored in environment variables. Students convert encoded attachments without installing extra software. Anyone can compare input and output sizes to verify compression ratios. The history panel tracks recent decodes for easy reuse.

Technical Details:

This section outlines the decoder’s key functions and underlying logic.

  • Accepts plain text, drag-dropped files, or clipboard input.
  • Automatically detects and fixes missing padding characters.
  • Handles URL-safe Base64 by translating - and _.
  • Displays input and output byte counts with live size ratio.
  • Maintains a history of the ten most recent decodes in local storage.
  • Supports Ctrl + Enter hotkey for quick copy actions.
  • Uses the browser’s native atob() and TextDecoder APIs for speed.

Micro Example

The string SGVsbG8= decodes to Hello.

Input Length (chars) Decoded Output Length (bytes)
SGVsbG8= 8 Hello 5

Step-by-Step Guide:

Follow these steps to decode data accurately.

  1. Paste or drag the Base64 text into the input area Tip.
  2. (Optional) Tick URL-safe if the string uses - or _.
  3. (Optional) Tick No padding if the string omits = characters.
  4. Review live byte statistics below the textarea.
  5. Copy the decoded result using the button or Ctrl + Enter.
  6. Open the history pane to reuse previous outputs Caution.

FAQ:

Find concise answers to common questions.

Why does my input produce empty output?

Invalid characters or incorrect padding cause decoding failures. Verify the string and enable padding repair if needed.

Is decoding performed offline?

Yes. All processing occurs in your browser. The tool never transmits data externally.

Does the decoder support large files?

The browser limits memory usage. Extremely large files may exhaust resources; consider chunked processing for safety.

What is URL-safe Base64?

It replaces + with - and / with _ to remain valid inside URLs.

Where is history stored?

The tool saves history in localStorage within your browser. Clearing site data removes the records.

Troubleshooting:

Resolve issues quickly using the guidance below.

  • Output garbled: Check the URL-safe checkbox to convert special characters.
  • Padding errors: Enable No padding to auto-append missing = signs.
  • Clipboard copy fails: Grant clipboard permission or copy manually from the textarea.
  • File will not load: Ensure the file contains Base64 text, not binary data. Rename if necessary.
  • Browser freezes: Split very large inputs into smaller chunks before decoding.

Advanced Tips:

Boost productivity with expert techniques.

  • Use query parameters to pre-populate the input for automated tests.
  • Combine with btoa() in DevTools to cross-verify round-trip fidelity.
  • Chain the decoder with browser bookmarks using javascript: URLs for one-click actions.
  • Leverage hotkeys in browser extensions to trigger instant decoding commands.
  • Store frequently decoded secrets in the history pane for repeat audits.

Glossary:

Clarify technical terminology used throughout the tool.

Base64
Binary-to-text encoding that maps three bytes to four ASCII characters.
Padding
= characters added to align the encoded length to a multiple of four.
URL-safe
Base64 variation that substitutes unsafe URL characters with safe alternatives.
Byte
A sequence of eight bits representing a single character or value.
Local Storage
Browser feature that stores key-value pairs persistently on the client side.
Embed this tool into your website using the following code: