How is this different from Extract a Substring?

This tool uses start/end index pairs, matching JavaScript's slice() method exactly. Extract a Substring instead uses a start position plus a length, matching substr()-style APIs. Use whichever matches how you're already thinking about the range.

What do negative indices do?

They count from the end of the string, so -1 refers to the last character, matching JavaScript's own slice() behavior exactly.

What if the end index is left blank?

The slice extends to the end of the string, the same default slice() uses when no end argument is given.

String Slicer Online - Extract Text by Index Range

Overview

Introduction

Extracting a piece of text by index is one of the most common string operations in code, and this tool mirrors JavaScript's own slice() semantics exactly, including negative index support.

It runs entirely client-side, so nothing you paste is ever uploaded to a server.

What Is String Slicer?

A substring extractor matching String.prototype.slice(start, end): positive indices count from the start, negative indices count from the end.

It runs entirely client-side as part of this site's String Tools collection, so nothing you paste is ever uploaded to a server.

How String Slicer Works

The input is split into an array of Unicode code points, sliced between the given start and end indices, and rejoined.

The transformation happens synchronously in JavaScript the moment you type, with no network round trip involved.

When To Use String Slicer

Use it to test what a slice(start, end) call would return before writing the equivalent code, or to quickly extract a known range from text.

It's a fast way to get the answer without opening a code editor, a REPL, or writing a one-off script just to check.

Often used alongside Substring Extractor and String Truncator.

Features

Advantages

Matches JavaScript's native slice() behavior exactly, including negative indices.
Operates on Unicode code points rather than raw UTF-16 units.

Limitations

Requires knowing the exact index range you want; for a fuzzy 'find this text' extraction, use Find and Replace or a regex tool instead.

Examples

Slicing a fixed range

Input

Hello, world!

Output

Hello

start=0, end=5 extracts the first five characters.

Slicing with a negative index

Input

Hello, world!

Output

world!

start=-6 extracts the last six characters, matching JavaScript's negative-index convention.

Best Practices & Notes

Best Practices

Use negative indices when you want to extract relative to the end without first computing the string's length.

Developer Notes

The implementation spreads the input into code points ([...input]) before slicing, so multi-byte characters like emoji aren't split apart the way a naive index into the raw UTF-16 string could.

String Slicer Use Cases

Testing a slice(start, end) expression before writing code
Extracting a known-position substring from text
Trimming a fixed number of characters from either end

Common Mistakes

Confusing this with substr()-style start+length semantics; use Extract a Substring for that instead.

Tips

Use Extract a Substring instead if you're thinking in terms of a starting position and a length rather than two indices.

String Slicer