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Base64 Encode / Decode

Use this base64 encode / decode calculator to convert compatible units or encoded values for base64 encode / decode.

Primary answer
Output text
Inputs to verify
Operation, Text, and Alphabet
Use type
Use as a direct calculation check.
Keyword intent
base64 encode / decode calculator

Calculator

Base64 Encode / Decode

Calculates output text from operation, text, alphabet. Defaults are filled in so you can review a working example before changing inputs.

Encode UTF-8 text to Base64 or decode Base64 text to UTF-8.

Plain text for encode mode, or Base64 text for decode mode. Empty text is valid.

Standard uses + and /. Base64url uses - and _.

Encoding follows this style; decoding accepts canonical padded or unpadded input.

Result

Result reflects the current submitted inputs.

  • Risk A
  • Reviewed 2026-05-26
  • 2 sources
Output textaGVsbG8gd29ybGQ=
Normalized Base64aGVsbG8gd29ybGQ=
UTF-8 byte length11 bytes
Character count11 chars
Output length16 chars
OperationEncode as standard Base64
  • This utility is text-only and uses UTF-8 bytes.
  • Standard Base64 uses + and /; Base64url uses - and _.
  • No MIME line wrapping is inserted or ignored.
  • Decode mode rejects whitespace, invalid alphabet characters, impossible padding, and non-UTF-8 byte sequences.

Accuracy notes

Risk level
A
Reviewed
2026-05-26
Sources
2
Primary result
Output text

Formula logic is kept in a pure calculator module with fixtures, source notes, and page-visible assumptions.

Categories

What the result means

Use Output text as the headline answer for base64 encode / decode. Encoded Base64 text or decoded UTF-8 text. Read the converted value first, then verify the source unit, target unit, and factor before reusing the number. Use normalized base64, UTF-8 byte length, and character count to explain why output text moved when an input changed. Keep the original value next to the converted value when using it in a workflow.

Output textEncoded Base64 text or decoded UTF-8 text.
Normalized Base64Canonical Base64 using the selected alphabet and padding style.
UTF-8 byte lengthByte length of the decoded text payload.
Character countUnicode code point count of the decoded text payload.

Use the result this way

  1. Start with Output text, then use supporting outputs only to explain the primary answer.
  2. Verify operation, text, and alphabet before copying the result.
  3. Choose the mode or method first because it can change which formula is applied.
  4. Keep the original value next to the converted value when using it in a workflow.

User job

How to use this calculator

Use Base64 Encode / Decode when you need output text, then use normalized base64 and utf-8 byte length to check the context for unit checks, engineering notes, recipes, travel, shopping, and measurement cleanup.

Best for

  • Converting compatible units
  • Auditing the factor used for a repeated conversion
  • Reviewing a default example before entering your own operation and text.

Check before relying

  • Make sure the source and target units measure the same kind of quantity.
  • This utility is text-only and uses UTF-8 bytes.
  • Standard Base64 uses + and /; Base64url uses - and _.
  • Source context: RFC Editor, reviewed 2026-05-26.

Next useful step

  • URL Encode / DecodeUse next when the developer utility comparison needs URL encode / decode inputs such as operation and text.
  • Binary CalculatorUse next when the developer utility task needs decimal instead of output text.
  • Hex CalculatorUse next when the developer utility task needs decimal instead of output text.

Formula

Encode UTF-8 bytes with the RFC 4648 Base64 or Base64url alphabet, or decode strict Base64 text back to valid UTF-8 text. Key assumptions: This utility is text-only and uses UTF-8 bytes. Standard Base64 uses + and /; Base64url uses - and _. No MIME line wrapping is inserted or ignored.

  • Encode UTF-8 bytes with the RFC 4648 Base64 or Base64url alphabet, or decode strict Base64 text back to valid UTF-8 text.
  • This utility is text-only and uses UTF-8 bytes.
  • Standard Base64 uses + and /; Base64url uses - and _.
  • Primary source context: RFC Editor.

Inputs

Enter operation, text, alphabet, and padding style for unit checks, engineering notes, recipes, travel, and measurement cleanup. Before calculating, choose the mode or method first because it can change which formula is applied. Operation: Encode UTF-8 text to Base64 or decode Base64 text to UTF-8. Text: Plain text for encode mode, or Base64 text for decode mode. Empty text is valid. Alphabet: Standard uses + and /. Base64url uses - and _. Padding style: Encoding follows this style; decoding accepts canonical padded or unpadded input.

OperationEncode UTF-8 text to Base64 or decode Base64 text to UTF-8.
TextPlain text for encode mode, or Base64 text for decode mode. Empty text is valid.
AlphabetStandard uses + and /. Base64url uses - and _.
Padding styleEncoding follows this style; decoding accepts canonical padded or unpadded input.

Example

Using the default inputs, Base64 Encode / Decode returns output text of aGVsbG8gd29ybGQ=. Adjust operation, text, alphabet, and padding style to match your own scenario.

FAQ

How is output text calculated here?

Encode UTF-8 bytes with the RFC 4648 Base64 or Base64url alphabet, or decode strict Base64 text back to valid UTF-8 text. The first assumption to check is: This utility is text-only and uses UTF-8 bytes.

What does Output text mean for base64 encode / decode?

Read the converted value first, then verify the source unit, target unit, and factor before reusing the number. Secondary values such as normalized base64, UTF-8 byte length, and character count are there to explain the primary answer, not to replace it.

What should I enter for Operation?

Encode UTF-8 text to Base64 or decode Base64 text to UTF-8. Choose the mode or method first because it can change which formula is applied.

How does Text change output text?

Plain text for encode mode, or Base64 text for decode mode. Empty text is valid. Changing it can alter output text because the formula uses the submitted inputs together. Also compare source unit, target unit, dimension compatibility, exchange or conversion rate, and rounding precision.

Why does the base64 encode / decode example show aGVsbG8gd29ybGQ= for output text?

The default inputs produce aGVsbG8gd29ybGQ= for output text. Treat that as a format and scale check, then replace every default value with your own inputs.

How do I avoid a base64 encode / decode unit-direction mistake?

Keep the original value beside the converted value, confirm both units measure the same quantity, and check whether rounding is acceptable for the task.

Sources

Last reviewed: 2026-05-26

  • Reviewed 2026-05-26
    RFC 4648: The Base16, Base32, and Base64 Data EncodingsRFC Editor. Base64/Base64url encode/decode algorithm and official fixture examples.
    Scope
    Base64 and Base64url alphabets, padding behavior, canonical encodings, and test vectors.
    Supports
    Base64/Base64url encode/decode algorithm and official fixture examples.
  • Reviewed 2026-05-26
    Encoding StandardWHATWG. Text-to-byte and byte-to-text assumptions for this text-only Base64 utility.
    Scope
    UTF-8 encoding and decoding behavior used by web platform TextEncoder and TextDecoder.
    Supports
    Text-to-byte and byte-to-text assumptions for this text-only Base64 utility.