The true power of regular expressions (2012)
The article discusses the capabilities of regular expressions in parsing HTML and other data formats. It explains the concept of regular grammars and how regular expressions can represent them more concisely. Additionally, it highlights the differences between formal definitions of regular languages and the practical implementations of regular expressions in programming languages.
- ▪Regular expressions can be powerful tools for parsing data, contrary to the common belief that they cannot parse HTML.
- ▪The article explains the formal definition of regular grammars and how they can be represented using regular expressions.
- ▪Modern regex implementations can match more than just regular languages, expanding their utility in programming.
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Record
| Original publisher | Npopov |
| Canonical URL | https://www.npopov.com/2012/06/15/The-true-power-of-regular-expressions.html |
| Publication time | Sat, 30 May 2026 08:12:01 +0000 |
| Retrieval time | 2026-05-30T08:42:09.002Z |
| Last seen | 2026-05-30T08:42:09.002Z |
| Headline source | Publisher (no WeSearch rewrite) |
| Excerpt source | publisher body |
| Excerpt method | First ~120 words (~800 chars) of extracted publisher body, fair-use limited. |
| Summary | WeSearch · cerebras-chat (WeSearch summarizer) |
| Summary source text | contentText |
| Citation coverage | Summary is a WeSearch-generated derivative; primary citation is the original publisher URL. |
| Cluster | 2moPFah5vbFZ |
| Cluster logic | Grouped by semantic title/content similarity across sources within a rolling window. Same-publisher template collisions are excluded from coverage comparison. |
| Ranking reason | Story pages are not engagement-ranked. Hub feeds use recency, with optional source-diversified chronological ordering (cap consecutive stories per source). No personalized ranking. |
| Publisher visit | Yes — open original |
| Substitutes article? | No — link-out required for full text |
Rights status (four layers)
WeSearch handling by dimension
| Indexing | May the item be indexed (stored, ranked, made findable)? | Allowed |
| Snippet | May a short excerpt of the publisher's text be shown? | Allowed |
| AI summary | May WeSearch generate its own short summary of the article? | Limited |
| Retrieval / RAG | May the content be exposed for third-party retrieval-augmented generation? | Not asserted |
| Model training | May the content be used to train AI models? | Not asserted |
| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
As someone who frequents the PHP tag on StackOverflow I pretty often see questions about how to parse some particular aspect of HTML using regular expressions. A common reply to such a question is: You cannot parse HTML with regular expressions, because HTML isn’t regular. Use an XML parser instead. This statement - in the context of the question - is somewhere between very misleading and outright wrong. What I’ll try to demonstrate in this article is how powerful modern regular expressions really are.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Npopov.
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