# Base64 UTF-8

`base64-utf8` · version 1.0.0 · Encoding & checksums · free, no key needed

Decode standard Base64 to UTF-8 text. Transformation only; no security claim.

**Use when you need to: base64 utf8 · base64 decode utf8 · decode base64 text.**

## Supported

- base64 utf8
- base64 decode utf8
- decode base64 text

## Not supported

- base64url
- ignore whitespace
- compression
- encryption

## Behavior

- Input must be standard Base64: alphabet A-Za-z0-9+/, length multiple of 4 (empty allowed), padding only at end as required, no whitespace.
- Reject URL-safe alphabet, missing padding, extra padding, and non-canonical leftover bits.
- Decoded bytes must be valid UTF-8; reject overlong encodings and invalid sequences.
- This is a byte transform, not confidentiality or authenticity.

## Input

- `base64` (string, required): max length 256000

## Output

- `text` (string, required)

## Limits

- max input bytes: 256000

## Example

Request input:

```json
{
  "base64": "TWFu"
}
```

Response:

```json
{
  "result": {
    "text": "Man"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "base64-utf8",
  "version": "1.0.0",
  "input": {
    "base64": "TWFu"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/base64-utf8/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"base64":"TWFu"}'
```

The machine-readable contract is at [/v1/tools/base64-utf8/versions/1.0.0](/v1/tools/base64-utf8/versions/1.0.0).

### CLI

```sh
node cli.mjs run base64-utf8 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [UTF-8 Base64](/tools/utf8-base64): Encode a Unicode string as standard Base64 of its UTF-8 bytes. Transformation only; no security claim.
- [UTF-8 hex](/tools/utf8-hex): Encode a Unicode string as lowercase hex of its UTF-8 bytes. Transformation only; no security claim.
- [Adler-32](/tools/adler32): Adler-32 of UTF-8 bytes (RFC 1950). Integrity check only; no security claim.
- [CRC-32](/tools/crc32): CRC-32 of UTF-8 bytes (ISO 3309 / ZIP / PNG polynomial). Integrity check only; no security claim.
- [Hex bytes concat](/tools/hex-bytes-concat): Concatenate a bounded ordered list of lowercase hex byte strings into one hex string.
- [Hex bytes slice](/tools/hex-bytes-slice): Slice a lowercase hex byte string by explicit byte-index bounds, half-open like Array.slice.