FormatFlow

No tool matches “”

Try a format (“webp”, “mp3”) or a verb (“merge”, “compress”).

PDF toolsImage toolsVideo toolsAll tools

Loading index

↵to open

Developer Tools · Updated October 19, 2026

Base64 Decoder

You can decode Base64 back into readable UTF-8 text, accept URL-safe or line-wrapped input, and save the decoded bytes as a file when the payload is not text.

Runs in your browserFree · No sign-up · No watermark
Base64TXTRuns in your browser
Loading the tool…

Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Formats
Base64 → TXT
Processing
In your browser
Max size
Up to 4 million Base64 characters
Price
Free, no account
Updated
October 19, 2026
All Developer Tools

About Base64 Decoder

Base64 appears anywhere bytes have to travel through a text-only channel: data URIs, email attachments, JSON payloads and JWT segments. Decoding it by hand is error-prone, and the browser's own atob function returns Latin-1, which turns accented text, Chinese and emoji into mojibake.

This decoder converts through UTF-8 properly and also handles the variations people actually paste: URL-safe letters, wrapped lines, spaces and missing padding. If the decoded bytes are not text, it says so, shows a hex preview and lets you save the bytes under a file name you choose.

What this tool does

The details that matter when you use Base64 Decoder for real work.

  • UTF-8-safe text output

    Bytes pass through TextDecoder, so accents, Chinese, Japanese and emoji decode correctly instead of becoming garbled Latin-1 characters.

  • Accepts real-world Base64

    URL-safe dashes and underscores are normalized, spaces and line breaks are ignored, and missing padding is restored before decoding.

  • Binary payload detection

    When the bytes are not valid UTF-8, the tool shows a hex preview instead of pretending they are text.

  • Save decoded bytes as a file

    Small binary payloads can be written to a local file under a name you choose, which is handy for images or archives sent as Base64.

  • Specific error messages

    Invalid characters, bad padding and truncated input each produce a message that names the problem instead of a generic failure.

  • Copy and sample

    Copy decoded text in one click, or load a sample string containing accents and an emoji to see how UTF-8 decoding works.

How to use Base64 Decoder

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Paste the Base64

    Paste the encoded string into the input; line breaks, spaces and URL-safe characters are all accepted.

  2. 02

    Press Decode

    The decoder validates the alphabet, normalizes padding and converts the bytes, showing an error if the string is not valid Base64.

  3. 03

    Read the decoded text

    If the bytes are valid UTF-8, the readable text appears in the output box and can be copied with one click.

  4. 04

    Save binary payloads

    For image, archive or other non-text payloads, give the file a sensible name and use Download file to save the bytes locally.

Supported formats and limits

Input
Base64
Output
TXT
Processing
Client-side, in your browser. Nothing is uploaded.
Maximum size
Up to 4 million Base64 characters
Requirements
Chrome, Edge, Firefox or Safari · JavaScript enabled

Limitations worth knowing

  • Input is capped at four million characters, and very large strings are limited by the memory available to the browser tab.
  • Base64 contains no file type information, so the decoder cannot choose the right extension for a binary payload for you.
  • Non-UTF-8 text, such as legacy single-byte encodings, is reported as binary rather than guessed.

Privacy and file handling

Decoding happens in this browser tab. The Base64 string and the decoded bytes never leave your device, nothing is stored or logged, and downloaded files are created locally by the browser.

Read the full privacy policy

Base64 Decoder FAQ

Short, direct answers to the questions people ask before using this tool.
Can the decoder handle URL-safe Base64 and missing padding?
Yes. Dashes and underscores are converted to the standard plus and slash characters, padding is added back where it is missing, and spaces or line breaks are ignored, so a JWT segment or a wrapped email body decodes without manual cleanup.
What happens if the Base64 contains an image or an archive?
The decoder still produces bytes, but they are not valid UTF-8 text, so the tool shows a hex preview and offers a file download. Name the file with the extension of the original payload, such as .png or .zip, before opening it.
Why does the decoder say the bytes are not valid UTF-8?
Base64 is used for every kind of file, not just text. If the archived bytes are not a valid UTF-8 sequence, showing them as text would display replacement characters or confuse you about the contents, so the decoder reports binary data instead.
How do I know which file extension a decoded payload should use?
Base64 carries no file type information, so the answer has to come from where the string was found, such as a data URI prefix or the filename in the email it arrived in. When unsure, save it as .bin and inspect it before opening.
How large a Base64 string can the decoder handle?
The input cap is four million characters, which is enough for most API payloads, data URIs and email bodies. Larger strings are better decoded with a command-line tool because a browser tab has to hold the encoded and decoded copies in memory.
Is it safe to decode Base64 copied from an email or log?
Decoding itself runs locally and cannot execute anything, but the decoded content may be malicious: an archive or document can still be dangerous when opened later. Treat unexpected attachments with caution and scan downloads before using them.
Why are line breaks inside Base64 not reported as errors?
Line breaks are not part of the Base64 alphabet, but MIME, PEM and some APIs wrap encoded data every 64 or 76 characters. The decoder removes all whitespace before validating, so wrapped strings decode normally.

Background reading

Format guides that explain the trade-offs behind Base64 Decoder.