Hyphens for Descriptive URL Paths vs Underscores for Technical URL Data: which should you choose?

Yes. The guidance represented here still identifies hyphens as the preferred word separator for descriptive URLs. That recommendation remains useful even as language understanding improves. Hyphens make term boundaries explicit and keep public paths consistent. For regulated sites, consistency also makes technical reviews easier to document.

Underscores do not create an automatic penalty or guarantee poor rankings. The concern is weaker clarity for separate terms inside a descriptive slug. Use hyphens to remove that avoidable ambiguity. Evaluate rankings through the complete page, linking, authority, and technical context rather than one character alone.

Do not migrate solely because a newer convention looks cleaner. First review current visibility, backlinks, internal links, canonicals, and operational risk. Underperforming or newly planned paths may justify standardization. Any approved change requires tested 301 redirects and updated internal references.

AI systems tokenize text and use surrounding signals to interpret sources. Hyphens present visible boundaries in a descriptive URL. A model such as GPT-4 can also use page content, links, and structured context. Treat the slug as one clarity signal, not independent proof of authority or citation eligibility.

Underscores are appropriate for non-SEO data that follows technical conventions. Examples include API values, database-linked identifiers, tracking parameters, and internal integration strings. Keep them outside descriptive public paths unless a documented system constraint requires otherwise.

Hyphens and underscores each occupy one character, so the separator itself does not create a meaningful length difference. Length grows when paths include unnecessary folders or filler terms. Keep the final slug concise, descriptive, and aligned with the page topic.