Base64 Decoder — Decode Base64 Strings Online Free
Text · Image · File — URL-safe mode · auto-detect · live image preview — 100% browser-side
Paste text → get Base64
Real-time · No button click · 200ms debounce
Paste any Base64 string to decode it back to text, image, or binary file — instantly. Auto-detects standard Base64 and URL-safe Base64URL. For image Base64, shows a live preview and lets you download the decoded file with the correct extension.
What is Base64 Encoding?
Base64 encoding converts binary data into a string of 64 safe ASCII characters — A–Z, a–z, 0–9, +, and /. It is the standard way to embed binary content (images, files, certificates) inside JSON, XML, HTML, and email without breaking the format. The encoded output is ~33% larger than the original.
Standard vs URL-Safe Base64
Standard Base64 uses + and / which have special meaning in URLs. URL-safe Base64 (Base64URL) replaces +→- and /→_ and removes = padding. Use URL-safe mode for JWT tokens, OAuth tokens, and URL query parameters.
Frequently Asked Questions
How do I decode a Base64 string back to text?
Set Direction to Decode and paste your Base64 string into the left panel. The decoded text appears instantly on the right. The tool auto-detects whether your input is standard Base64 or URL-safe Base64URL and handles both.
How do I decode a Base64 image back to the original file?
Switch to the Image tab, paste your Base64 string or data URI in the Decode section. The tool detects the image type (JPEG, PNG, GIF, WebP) from magic bytes and shows a live preview. Click Download to save the image file.
What if my Base64 decoding returns garbled text?
Garbled output usually means the original binary was not UTF-8 text — it may be an image, PDF, or other binary file. Switch to the File tab to decode it as a binary file and download with the correct extension.
What is the difference between Base64 and Base64URL decoding?
Standard Base64 uses + and / with = padding. URL-safe Base64 uses - and _ with no padding. Enable the URL-safe toggle or the tool auto-detects and switches automatically based on your input characters.
Can I decode a data URI with this tool?
Yes — paste the full data URI (data:image/png;base64,...) into the Image decode section. The tool strips the prefix, auto-detects the MIME type, and shows a live preview.