How do I specify multiple terms?

Enter them separated by commas, like 'cat, dog, bird', and every occurrence of any of them is wrapped with the marker in a single pass.

Does it match whole words only?

No, this tool matches the terms as substrings anywhere they appear, unlike the Word Highlighter which requires whole-word boundaries.

What happens if one term contains another?

Longer terms are matched first internally, so a longer term isn't shadowed or split apart by a shorter term it contains.

Multi-Pattern Highlighter - Mark Several Terms at Once

Overview

Introduction

Scanning a document for several different keywords at once, like a list of flagged terms or entities, is much slower to do by eye one term at a time.

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

What Is Multi-Pattern Highlighter?

A multi-pattern highlighter that wraps every occurrence of any term from a comma-separated list with a marker string on both sides, matched case-insensitively.

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 Multi-Pattern Highlighter Works

The comma-separated terms are trimmed, escaped for safe regex use, sorted longest-first, and combined into a single alternation pattern so every occurrence of any term is wrapped with the marker in one pass.

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

When To Use Multi-Pattern Highlighter

Use it to spot several different keywords, entity names, or flagged terms across a document at once, without running a separate tool per term.

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 Word Highlighter and Letter Highlighter.

Features

Advantages

Highlights an unlimited number of different terms in a single pass.
Sorts terms longest-first internally to avoid a shorter term shadowing a longer one.
Escapes every term before assembling the pattern, so a search term containing regex characters such as a full stop or a bracket is matched literally.

Limitations

Matches terms as substrings, not whole words only, so a short term can match inside unrelated longer words.
Applies the same marker to every term, so the output shows where the matches are but not which term produced each one.

Examples

Highlighting several terms

Input

The cat chased the dog around the yard

Output

The **cat** chased the **dog** around the yard

Both 'cat' and 'dog' from the term list are wrapped, while other words are untouched.

Best Practices & Notes

Best Practices

Use the Word Highlighter instead when you only need whole-word matching for a single term.
Include the longest and most specific terms even when shorter ones overlap them, since the longest-first sorting guarantees the specific match wins.
Choose a marker that appears neither in the text nor in any of your terms, otherwise the result becomes ambiguous to read.

Developer Notes

Terms are escaped with `term.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")`, sorted with `.sort((a, b) => b.length - a.length)`, and joined into `new RegExp(`(${escaped.join("|")})`, "gi")`, so the alternation tries longer terms before their shorter substrings.

Multi-Pattern Highlighter Use Cases

Spotting several flagged keywords or entity names across a document
Highlighting a set of related terms for a presentation or report
Reviewing text for multiple search terms at once

Common Mistakes

Expecting whole-word-only matching; short terms can match inside longer unrelated words.
Forgetting the comma-separated format when entering multiple terms.

Tips

List related terms together, like synonyms or variants of a keyword, to see their combined coverage in one highlighted pass.
Adding a leading space to a term is a rough way to force whole-word matching when a short term keeps matching inside longer words.

Multi-Pattern Highlighter