Base64 编解码
在浏览器中 Base64 编码与解码
Input
Output
Encode and decode Base64 without trusting an online server
Base64 shows up everywhere — JWT payloads, image data URIs, email attachments, API request bodies. Encoding and decoding it in your browser keeps the data on your machine, which matters when the value is a token, a secret, or anything else you'd rather not paste into a remote service.
Use the tool when you need to
Decode a Base64-encoded value from a header
Inspect Authorization headers, encoded query parameters, or other Base64 strings safely in the browser.
Encode binary data for an API
Convert a small image or file into a Base64 string for inclusion in a JSON request body.
Flip between Base64 and Base64URL
Switch encoding variants when working with JWTs and URL-safe payloads.
How to encode or decode Base64 quickly
- 1
Paste the input into the text area.
- 2
Click Encode or Decode based on the direction you need.
- 3
Copy the result, or download it as a file when working with binary data.
Keep going
Encode URL components
Use percent-encoding when the destination is a URL rather than binary safety.
Decode JWTs
Use the focused decoder when the Base64 value is part of a token.
Format decoded JSON
Beautify the output if the decoded value turns out to be JSON.
Validate decoded JSON
Confirm the decoded JSON parses cleanly before passing it forward.
Common Base64 workflows
Decode a Basic auth header to see the raw username and password format being sent.
Encode a tiny image as a data URI and embed it directly in an API request body.
Decode a JWT segment, edit it, and re-encode it for testing — without server-side help.
相关工具
常见问题
Base64 会把二进制数据编码成 ASCII 文本，使用 64 个可打印字符（A-Z、a-z、0-9、+、/）。常用于在 JSON、XML、HTML、邮件等纯文本格式里嵌入二进制内容。编码后体积通常会比原始数据大约增加 33%。
把文本粘贴到输入框，点击 Encode。工具会先按 UTF-8 将字符转成字节，再转换为 Base64。点击 Copy 可复制结果。
常见场景：在 CSS/HTML 里内嵌小图片（data URI）、在 JSON API 中传输二进制数据、上传时对文件内容做编码、邮件附件（MIME）、在只支持文本的数据库中存储二进制内容。
标准 Base64 使用 + 和 /，放到 URL 里往往需要转义。Base64URL 用 - 和 _ 替换它们，并且通常去掉填充符号（=）。JWT 常用 Base64URL，因为 token 经常会出现在 URL 中。