What is this Base64 encoder for?
This Base64 encoder converts plain text, files, JWT payloads, and image data into or out of Base64 directly in your browser. It is best for developers, support teams, and technical users who need quick encoding, URL-safe Base64, data-URI conversion, or private client-side decoding without uploading data.
Base64 is useful when a system expects text but you need to carry bytes, structured JSON, an image, or another file-safe representation through it. The format is common in email attachments, HTTP APIs, CSS data URLs, authorisation headers, SAML responses, and debugging logs. This page keeps the conversion controls at the top for quick work, then gives practical notes so you can choose the right Base64 variant and avoid treating encoding as security.
Last updated: August 11, 2026
Input
Output
Additional Tools
JWT Decoder
Decode and inspect JWT tokens
Image to Data-URI
Convert images to Base64 data-URIs for CSS/HTML embedding
URL Base64
Encode/decode URL-safe Base64 (RFC 4648)
Bulk Processor
Encode/decode multiple lines at once
History
About Base64
What is Base64?
Base64 is a binary-to-text encoding scheme that represents bytes with a limited ASCII alphabet: uppercase letters, lowercase letters, numbers, plus, slash, and equals signs for padding. It was designed for channels that handle text reliably but may not safely carry raw binary data.
Common Uses
- Encoding binary files for email transmission
- Data-URIs in CSS and HTML
- API authentication tokens
- JWT and SAML tokens
- Secure data transmission
Encoding Size
Base64 increases data size by ~33%. For example, 3 bytes of binary data becomes 4 Base64 characters.
How Base64 encoding works
Base64 groups the original bytes into blocks of three, producing 24 bits at a time. Those 24 bits are split into four 6-bit values, and each value is mapped to one printable character from the Base64 alphabet. If the final block has only one or two bytes, equals signs are added as padding so the output length still fits the four-character grouping.
For a short text example, the word Hello becomes SGVsbG8=. The visible letters are not encrypted or hidden; they are simply a different representation of the same bytes. If you paste SGVsbG8= into decode mode, the browser reconstructs the original UTF-8 text and displays Hello.
The URL-safe option follows RFC 4648 by replacing + with - and / with _. Many systems also remove trailing padding when a Base64 value is placed in a URL path, query parameter, filename, or JSON Web Token segment. This tool accepts padded and unpadded URL-safe strings and adds any missing padding before decoding.
Step-by-step guide
Encode text
Select Encode, paste API key: demo-123 into the input field, and copy the generated output QVBJIGtleTogZGVtby0xMjM=. Use this when a test fixture, documentation sample, or API request needs a Base64 string instead of plain text.
Decode text
Select Decode and paste eyJzdGF0dXMiOiJvayJ9. The output is {"status":"ok"}. If decoding fails, check for accidental spaces, missing characters, or a value that is compressed, encrypted, or URL encoded before Base64 was applied.
Use URL-safe mode
Turn on URL-safe mode when the value will sit inside a URL, filename, cookie value, or JWT segment. For example, bytes that would normally produce +w== may be written as -w in URL-safe form.
Convert images
Choose Image to Data-URI, select a small image, and copy the generated data:image/...;base64, string. This is practical for tiny icons or single-file prototypes, but large images should usually remain separate assets so pages stay cacheable and easy to maintain.
Inspect JWTs
Paste a JWT and use Decode JWT to inspect the header and payload. The tool decodes the readable segments, but it does not verify the signature or tell you whether the token is trustworthy. Treat any token shown in a browser as sensitive.
Process batches
Put one value per line and use the bulk processor when you need to convert a list of test identifiers, fixture values, or log snippets. Each line is handled separately so one malformed value is easier to spot.
Worked examples
| Task | Input | Output | When it helps |
|---|---|---|---|
| Encode a greeting | Hello, world! |
SGVsbG8sIHdvcmxkIQ== |
Quickly confirm that an integration expects standard Base64 text. |
| Decode JSON | eyJyb2xlIjoiYWRtaW4ifQ== |
{"role":"admin"} |
Read a configuration snippet, fixture, or token payload during debugging. |
| Decode URL-safe text | SGVsbG8tdXJsX3NhZmU |
Hello-url_safe |
Check values copied from URLs, route parameters, or JWT segments. |
| Build a data URL | small logo file |
data:image/png;base64,... |
Embed a tiny asset in a prototype, email template, or CSS proof of concept. |
Practical use cases
API development
Developers often need Base64 for basic authentication headers, binary-safe JSON fields, sample payloads, and mocked webhook events. Keeping the conversion in the browser makes it fast to verify examples while writing documentation or tests.
Support and incident response
Support teams can decode a copied payload, check whether it is plain JSON, and decide whether to escalate to engineering. Because the tool is client-side, the entered text is not uploaded to a conversion endpoint.
Frontend prototyping
Small SVGs, icons, and placeholders can be converted into data URLs for quick prototypes. The trade-off is file size: Base64 is larger than the original bytes and prevents the browser from caching the asset separately.
Security reviews
Base64 often appears in tokens, logs, and suspicious strings. Decoding can reveal whether a value is harmless text, structured data, or another encoded layer, but it should never be treated as proof that the data is authentic.
Base64 guides on this site
These internal guides give more context for common Base64 decisions:
Frequently Asked Questions
How do I encode text to Base64?
Simply paste your text into the Input field, make sure "Encode" mode is selected, and the tool will instantly convert it to Base64. You can then copy or download the encoded result.
What is Base64 encoding used for?
Base64 encoding is used to convert binary data into a text format that can be safely transmitted over text-only channels like email. It's also used for data-URIs in CSS, JWT authentication tokens, and SAML assertions.
Can I decode a JWT token with this tool?
Yes! This tool includes a dedicated JWT decoder. Paste your JWT token and click "Decode JWT" to inspect the header, payload, and signature. The JSON payload will be displayed and parsed for easy reading.
How do I convert an image to a data-URI?
Use the "Image to Data-URI" tool. Upload your image file, and the tool will convert it to a Base64-encoded data-URI that you can embed directly in HTML or CSS without needing a separate image file.
Is URL-safe Base64 different from standard Base64?
Yes. URL-safe Base64 (RFC 4648) uses hyphens (-) and underscores (_) instead of plus signs (+) and forward slashes (/). This makes it safe for use in URLs and filenames. Toggle "URL-safe mode" to encode using this standard.
Can I process multiple lines at once?
Yes! Use the "Bulk Processor" tool to encode or decode multiple lines simultaneously. Each line is processed independently, making it perfect for batch operations.
Is my data secure when I use this tool?
Yes. All encoding and decoding happens entirely in your browser using JavaScript. Your data is never sent to our servers. The tool works completely offline once loaded.
Does Base64 encoding provide encryption?
No. Base64 is an encoding scheme, not an encryption method. It makes binary data readable as text, but it offers no security. Anyone can easily decode Base64 back to its original form. For secure data, use actual encryption algorithms like AES.
Why does Base64 output sometimes end with equals signs?
Equals signs are padding. They show that the final byte group was shorter than three bytes, so the encoder filled the four-character output block. Some URL-safe systems remove padding, but standard Base64 commonly keeps it.
Why is my decoded output unreadable?
The original data may be binary, compressed, encrypted, or not UTF-8 text. Base64 can represent any bytes, so decoding does not guarantee a human-readable result. If the source was an image, archive, or encrypted value, you need the correct file format or decryption step after decoding.
Can I use Base64 for passwords or secrets?
No. Base64 is reversible by design. It is acceptable for transport formatting, but secrets should be protected with proper hashing, encryption, access controls, and secure storage practices.
Does this tool upload files that I convert?
No. File reading uses browser APIs on your device. The resulting encoded text appears in the output field, and you choose whether to copy or download it.