> For the complete documentation index, see [llms.txt](https://hub.bsvblockchain.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hub.bsvblockchain.org/wiki/v/varint.md).

# VarInt

A **VarInt** (variable length integer) is a compact encoding used throughout the Bitcoin protocol to represent an integer using as few bytes as possible, depending on the value being represented. VarInts are commonly used to encode the length of a following list or array of items, such as the number of transactions in a block or the number of inputs/outputs in a transaction, so that small values do not waste space on unnecessary leading zero bytes. A VarInt is encoded as follows:

| Value range                                                                                                                                                                                                                         | Encoding                                                                   |
| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------- |
| 0 to 252                                                                                                                                                                                                                            | A single byte containing the value.                                        |
| 253 to 0xffff                                                                                                                                                                                                                       | The byte `0xfd`, followed by the value as a 2-byte little-endian integer.  |
| 0x10000 to 0xffffffff                                                                                                                                                                                                               | The byte `0xfe`, followed by the value as a 4-byte little-endian integer.  |
| 0x100000000 to 0xffffffffffffffff                                                                                                                                                                                                   | The byte `0xff`, followed by the value as an 8-byte little-endian integer. |
| This encoding ensures that the vast majority of values seen in practice (such as small transaction or input/output counts) require only a single byte, while still allowing arbitrarily large values to be represented when needed. |                                                                            |


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://hub.bsvblockchain.org/wiki/v/varint.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.