Base64 Encoder Decoder Tool - Text and File Base64 Encoding with Data URI Support

First Published:
Last Updated:

Free Base64 Encoder and Decoder for text and files. All encoding and decoding processes are performed entirely within your browser - during the use of this tool, your data never leaves your device or gets uploaded to any server.

  • This tool is provided "AS IS" without any warranties of any kind.
  • The author accepts no responsibility for data loss or corruption during encoding/decoding.
  • Base64 encoding is NOT encryption — it does not provide any security or confidentiality.
  • Always keep backups of your original data.
  • By using this tool, you accept full responsibility for any outcomes.

Privacy: This tool uses client-side JavaScript for all processing. No data is transmitted to servers, no files are uploaded online, all processing happens locally in your browser. Once loaded, this tool continues to work even without an internet connection. For more details, please refer to our Web Tools Disclaimer.

Image Preview

Image preview

Features:

  • Text Encoding: Convert any text (including Unicode) to Base64 with full UTF-8 support.
  • Text Decoding: Decode Base64 strings back to readable text with proper UTF-8 handling.
  • URL-Safe Base64: Option to produce URL-safe Base64 output (RFC 4648 Section 5).
  • File Encoding: Encode any file (images, PDFs, documents) to Base64 using the FileReader API.
  • Data URI Generation: Copy Base64 as complete Data URIs (data:mime/type;base64,...) for embedding in HTML or CSS.
  • Image Preview: Instantly preview Base64-encoded images after encoding or decoding.
  • MIME Type Detection: Automatically detects file types from magic bytes (PNG, JPEG, GIF, WebP, PDF, ZIP, and more).
  • File Download: Download decoded binary data as a file with the correct extension.
  • 100% Client-Side: All processing happens in your browser. No data is transmitted to any server.
  • Works Offline: Once loaded, the tool works without an internet connection.

How to Use:

  1. Encode Text: Go to the "Text" tab, enter text in the left "Plain Text" area, and click "Encode →".
  2. Decode Text: On the same tab, paste a Base64 string in the right "Base64 Encoded" area and click "← Decode".
  3. Encode a File: Go to the "File" tab, select a file — it will be automatically encoded to Base64 in the right area.
  4. Decode Base64 to File: Paste Base64 or Data URI in the right area of the "File" tab and click "← Decode". Text content appears on the left; binary data can be downloaded.
  5. Download as Base64 Decoded File: After encoding or decoding, click "Download as Base64 Decoded File" to decode the Base64 data and save it as a file with the correct extension.
  6. URL-Safe Mode: Check the "URL-safe Base64" option before encoding to produce output suitable for URLs and filenames.

Important Notes:

  • Base64 encoding increases the data size by approximately 33%. This is expected behavior, not a bug.
  • Base64 is an encoding scheme, not encryption. It does not provide any security or confidentiality for your data.
  • Unicode text is handled via TextEncoder/TextDecoder APIs for correct UTF-8 encoding.
  • The maximum file size for encoding is 50 MB. Larger files may cause browser memory issues.
  • Data URIs generated by this tool can be used directly in HTML <img> tags, CSS url() values, or embedded in web pages.
  • Both standard Base64 (RFC 4648 Section 4) and URL-safe Base64 (RFC 4648 Section 5) are supported.

References:
Tech Blog with curated related content
Web Tools Collection

Written by Hidekazu Konishi