How is this different from Truncate a Text File?

Truncate always keeps the beginning up to a maximum size, while Slice extracts an arbitrary [start, end) byte range from anywhere in the file, letting you pull out a middle or trailing section.

What happens if I request a range past the end of the input?

The end offset is clamped to the input's actual byte length, so requesting more than exists simply returns everything up to the end.

Are start and end byte offsets or character offsets?

Byte offsets, measured in the input's UTF-8 encoding, which matters once the text contains any non-ASCII characters.

Text File Slicer - Extract a Byte Range from a File

Overview

Introduction

Sometimes you need one specific chunk out of a larger file, a header section, a middle segment, or everything after a known offset, not the whole thing truncated from the start.

This tool extracts exactly that byte range from pasted text.

What Is Text File Slicer?

A byte-range extractor that pulls the bytes between a start and end offset out of the input text, comparable to running dd skip=/count= or tail -c +N | head -c M on a file.

It operates on the UTF-8 byte encoding of the text, entirely in your browser.

How Text File Slicer Works

The input is encoded to UTF-8 bytes, the start and end offsets are clamped to the valid range, and the byte array is sliced between them.

Both the start and end cut points are individually backed off away from any multi-byte continuation byte they land on, so the decoded output is always valid text rather than a corrupted character at either edge.

When To Use Text File Slicer

Use it to pull a known section out of a larger text file, extracting a header, a fixed-offset record, or everything after a certain point.

It's also useful for reproducing what a byte-range HTTP request (Range: bytes=start-end) would return from a text resource.

Often used alongside String Slicer, Text File Truncator and Substring Extractor.

Features

Advantages

Extracts any arbitrary range, not just from the beginning.
Protects both edges of the slice from splitting multi-byte characters.
Runs entirely client-side.

Limitations

Offsets are byte-based, so they need to be computed against the UTF-8 size, not the character count, when the text isn't plain ASCII.
Backing off from a continuation byte can make the actual slice a few bytes narrower than requested at either edge.

Examples

Extracting a middle section

Input

0123456789ABCDEFGHIJ, start: 5, end: 10

Output

Bytes at offsets 5 through 9 are extracted; offset 10 is exclusive, matching typical [start, end) range semantics.

Best Practices & Notes

Best Practices

Compute offsets against the actual UTF-8 byte size of your source file, not its character count, if it contains non-ASCII text.
Use Truncate a Text File instead when you only need everything up to a maximum size from the start.
Chain with Damage a Text File to test how a downstream tool handles a corrupted version of the same slice.

Developer Notes

Both edges reuse the same continuation-byte back-off logic as Truncate a Text File, applied independently to start and end, which keeps the two tools' truncation behavior consistent.

Text File Slicer Use Cases

Extracting a specific record or section from a larger text file
Reproducing an HTTP byte-range request against local text
Isolating a known-offset header from a file for inspection

Common Mistakes

Using character offsets when the target system expects byte offsets, producing a slice that's off by however many multi-byte characters precede it.
Setting end lower than start, which the tool rejects rather than silently returning an empty or reversed result.

Tips

If you only know a character position, encode the text up to that point separately to find its byte offset before slicing.
Leave end larger than the input's actual size to mean 'to the end' without needing to know the exact byte length in advance.

Text File Slicer