# Bech32 convert bits

`bech32-convert-bits` · version 1.0.0 · Encoding & checksums · free, no key needed

Regroup integers between bit widths using BIP 173 rules, rejecting bad leftover padding.

**Use when you need to: convert 8 bit bytes into 5 bit bech32 symbols · convert 5 bit symbols back into 8 bit bytes · regroup integers from one bit width to another.**

## Decide before calling

Read the [versioned contract](/v1/tools/bech32-convert-bits/versions/1.0.0) and the supported scope below. Reuse `bech32-convert-bits@1.0.0` when your input, required output and limits match it. Choose another approach for an unsupported operation.

## Explain the choice

"I can use `bech32-convert-bits@1.0.0` for convert 8 bit bytes into 5 bit bech32 symbols. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

## Supported

- convert 8 bit bytes into 5 bit bech32 symbols
- convert 5 bit symbols back into 8 bit bytes
- regroup integers from one bit width to another
- reject non-zero leftover padding
- bip 173 convertbits with an explicit pad flag
- zero-pad leftover bits when the pad flag is true
- change bit grouping without adding a checksum
- expand bytes to the bech32 symbol width

## Not supported

- append or check a bech32 checksum
- parse an address string or human-readable part
- apply segwit witness version rules
- encode the Bech32 character set

## Behavior

- Implements BIP 173 convertbits. from_bits and to_bits are integers 1 through 8. pad is required: true emits one final zero-padded symbol when bits remain; false rejects that remainder.
- Each input integer must be in 0 .. 2^from_bits-1. Negative zero, NaN, and Infinity are rejected. The input array is not modified.
- pad false fails with invalid_input reason invalid_padding when leftover bits are at least from_bits wide, or when the leftover bits are non-zero. Zero leftover narrower than from_bits is accepted.
- There is no checksum and no HRP. 8-to-5 with pad true is the grouping used before Bech32 encoding; 5-to-8 with pad false is the grouping used after decoding.
- More than 256 input items, or more than 1024 output items, is limit_exceeded. The input length is checked before item values.
- Disclaimer: format transform only; provides no confidentiality, integrity, or authenticity.

## Input

- `data` (array of integer, required): max items 256; each min 0; each max 255
- `from_bits` (integer, required): min 1; max 8
- `to_bits` (integer, required): min 1; max 8
- `pad` (boolean, required)

## Output

- `data` (array of integer, required): max items 1024; each min 0; each max 255
- `to_bits` (integer, required): min 1; max 8

## Limits

- max items: 256
- max output items: 1024

## Example

Request input:

```json
{
  "data": [],
  "from_bits": 8,
  "to_bits": 5,
  "pad": true
}
```

Response:

```json
{
  "result": {
    "data": [],
    "to_bits": 5
  }
}
```

## How to call it

### MCP

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

```json
{
  "id": "bech32-convert-bits",
  "version": "1.0.0",
  "input": {
    "data": [],
    "from_bits": 8,
    "to_bits": 5,
    "pad": true
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/bech32-convert-bits/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"data":[],"from_bits":8,"to_bits":5,"pad":true}'
```

The machine-readable contract is at [/v1/tools/bech32-convert-bits/versions/1.0.0](/v1/tools/bech32-convert-bits/versions/1.0.0).

### CLI

```sh
node cli.mjs run bech32-convert-bits 1.0.0 --input input.json --base-url https://computefirst.net
```

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

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- [Bech32 validate](/tools/bech32-validate): Check Bech32 or Bech32m text and return a reason, without throwing when the checksum fails.
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