Base64 Decoder
Free online Base64 decoder — decode Base64 strings back to plain text instantly in your browser. Validates input and shows decoded payload size.
Updated June 2026
How to decode Base64 online
Three steps, no sign-up
1. Paste the string
Raw Base64, Base64URL, or a full data URL — the `data:...;base64,` prefix is stripped automatically.
2. See the result instantly
Decoding runs as you type and flags whether the string is valid or missing padding.
3. Copy or download
Text goes straight to your clipboard; binary content (PDF, XLSX, image…) turns into a file with the correct extension.
What this Base64 decoder does
More than plain-text decoding
Decodes to UTF-8 correctly
Uses TextDecoder on the actual bytes instead of raw atob() — accented letters and emoji come out intact.
Detects binary files
Reads the magic bytes of the decoded output and recognizes PDF, PNG, JPEG, GIF, WebP, ZIP (XLSX/DOCX/PPTX), XLS, and GZIP.
Downloads the original file
When the content is binary, a Download file button saves the result with the right extension already filled in.
Strips the data URL prefix
Paste data:application/pdf;base64,... directly — the data:<mime>;base64, prefix is removed automatically before decoding.
Fixes Base64URL and padding
Swaps -/_ for +// and fills in missing = characters before decoding, so JWTs and URL-safe strings just work.
Runs 100% in your browser
Nothing is sent to a server — decoding happens locally, including while offline.
Examples
What goes in, what comes out
When you'll reach for this tool
The most common scenarios among people who use it
PDF returned by an API
An invoice or contract comes back as a string inside a JSON response. Paste it and download the real PDF.
XLSX spreadsheet
Financial reports and integrations often return Excel files encoded as Base64.
JWT payload
Paste the middle segment of a token to read its claims: user, expiration, and roles.
Automation webhooks
n8n, Zapier, and Make deliver attachments as Base64. Inspect them before you act on the data.
CI/CD secrets
Check the value stored inside a Kubernetes secret or a GitHub Actions secret.
MIME email attachments
Bodies and attachments inside .eml files are Base64-encoded. Decode and download them.
Nothing decoded? Start here
The most common reasons a Base64 string won't decode
Base64URL string
If it came from a JWT or a URL parameter, swap - for + and _ for / before pasting.
Missing padding
Some systems strip the trailing = characters. Add them back until the length is a multiple of 4.
Hidden whitespace
Copying from PDFs or rich-text editors sometimes carries invisible characters along. Paste as plain text instead.
Characters outside the Base64 alphabet
The standard alphabet is only A–Z, a–z, 0–9, +, /, and =. A stray % or space breaks the decode.
Why decode Base64 here
Decoding happens entirely in your browser — no byte leaves your machine, and the page keeps working offline once it's loaded.
Unlike atob() in the console, this tool already handles UTF-8, Base64URL, missing padding, and file-type detection — you don't have to remember any of those edge cases every time. And even though everything stays local, if your security policy forbids pasting production secrets into online tools, use your browser console or a local CLI instead.
Quick Tools vs. the alternatives
They all decode; not all of them handle everything
Frequently asked questions
Paste the Base64 string — raw or with the data:application/pdf;base64, prefix, both work. The tool detects the PDF's magic bytes and shows a Download file button so you get back the original document.
References
Related Tools
- Base64 Encoder Developer Encode any text or string to Base64 instantly in your browser. Supports UTF-8, shows character count and output payload size. Free, no signup, 100% client-side.
- Base64 to Image Developer Paste a Base64 string or data URL and instantly preview the decoded image — free online converter supporting PNG, JPEG, WebP, GIF, SVG. No upload, runs locally.
- HTML Entity Decoder Developer Decode HTML entities to plain text online — unescape <, >, &, " and all named entities instantly in your browser.
- Image to Base64 Developer Upload any image and convert it to a Base64 data URL ready for HTML, CSS, or JSON — free online converter supporting PNG, JPEG, SVG, WebP. No server upload.
- URL Decoder Developer Decode any percent-encoded URL or string back to plain text instantly in your browser. Follows RFC 3986. Free, no sign-up required.
