Base64 string encoder/decoder

THE PRACTICAL GUIDE · NORMANDIN SYSTEMS

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Base64 string encoder/decoder converts text strings to Base64 text. Text is first represented as bytes and then encoded into the Base64 alphabet. Decoding reverses the Base64 stage before interpreting those bytes as text. Base64 is an encoding, not encryption. URL-safe Base64 uses a modified alphabet, so check the expected variant and padding convention. Preserve whitespace intentionally; a trailing newline is part of the data and changes the encoded result. Use the worked example to understand what a successful result looks like, then compare it with a small sample of your own input. Keep the original available until you have checked the output in its destination. Conversion establishes a representation; it does not establish that the underlying information is correct or that the receiving application accepts every supported feature.

Guide updated October 13, 2026

How to use this tool

1. Enter or load text strings using the input controls. Begin with the worked example or a small sample for which you know the expected result.
2. Review any available conversion options, then inspect the Base64 text result. Resolve a reported parse error at its source before attempting to reuse the output.
3. Check the example below against your own data. Preserve whitespace intentionally; a trailing newline is part of the data and changes the encoded result.
4. Copy or save the resulting Base64 text content using the controls provided, then validate it in the application or parser that will actually consume it.

SEE IT IN PRACTICE

A worked example

Hello

SGVsbG8=

This simple ASCII example has one byte per character. Accented letters and emoji can require several UTF-8 bytes.

Encoding text beyond ASCII

ASCII examples hide the character-encoding stage because each character uses one byte. UTF-8 encodes many other characters using several bytes, which changes the Base64 length. If decoding yields replacement characters or mojibake, check the original byte encoding. Re-encoding corrupted text cannot recover bytes that were already interpreted incorrectly and discarded.

Padding, alphabets, and line breaks

Standard Base64 uses letters, digits, plus, and slash, with equals signs used as padding at the end when needed. URL-safe Base64 replaces plus and slash with minus and underscore; some consumers also omit padding. These variants are not automatically interchangeable. Match the receiving protocol’s alphabet and padding rule rather than editing characters experimentally. Whitespace in the original text is data, so encoding Hello followed by a newline does not produce the same value as encoding Hello alone.

When this tool is useful

• Prepare text payload examples while retaining a separate copy of the source.
• Use a small example to troubleshoot character-encoding and padding errors and identify a representation mismatch.
• Create readable test vectors for APIs without manually rewriting every field or symbol.

Tips for a better result

• Base64 is an encoding, not encryption. URL-safe Base64 uses a modified alphabet, so check the expected variant and padding convention.
• Preserve whitespace intentionally; a trailing newline is part of the data and changes the encoded result.
• After changing formats, compare meaningful values rather than whitespace alone. Read the Base64 text output with its intended parser when exact types or escaping matter.

Frequently asked questions

Further reading

• RFC 4648: Base encodings