Regex search over website source code

Published December 9, 2025 · Regex · 2 min read

Wrap a pattern in slashes: /pattern/. Keep a literal fragment of at least three characters in it (like UA-) so the pre-filter stays fast, then let the regex handle the variable part.

Reach for regex when the thing you're hunting has a shape rather than a fixed value: an ID with a variable number, a CDN path with a version in it, a config key whose value changes per site. Wrap the pattern in slashes and SearchWebCode runs it against the raw source.

A speed rule first

The engine pre-filters candidates on literal 3+ character substrings, then verifies with your full regex. So anchor every pattern on a fixed fragment. /UA-[0-9]{4,}-[0-9]/ is fast because UA- narrows the field; a pattern that starts with /[a-z]+/ has nothing to pre-filter on and scans far more. Give it a literal handle.

Patterns that earn their keep

Legacy Analytics IDs: /UA-[0-9]{4,}-[0-9]/ — every Universal Analytics property by shape.
AdSense publisher IDs: /ca-pub-[0-9]{10,}/ — link sites to one Google Ads publisher account.
Meta Pixel inits: /fbq\(.init., .[0-9]{6,}/ — any Facebook pixel initialization.
Versioned libraries: /jquery-3\.[0-9]+\.[0-9]+/ — pin down which jQuery 3.x builds are in the wild.

Literal vs regex

If you know the exact value, search it literally — it's faster and needs no escaping. Use regex only for the variable part. For a full operator list including how regex composes with boolean AND/OR, see the syntax reference.

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Frequently asked questions

How do I run a regex search?

Wrap the pattern in slashes, e.g. /UA-[0-9]{4,}-[0-9]/, or toggle regex in the search box. It runs against the raw HTML/CSS/JS source.

Why is my regex slow?

The engine pre-filters on literal 3+ character fragments. A pattern with no fixed substring (like /[0-9]+/) has nothing to narrow on and scans much more. Anchor it on a literal like UA- or ca-pub-.

Can I mix regex with AND/OR?

Yes — a /regex/ term can be one leaf of a boolean query, e.g. combined with a literal via a space (AND) or OR. See the syntax reference.