How we verify

In short

Only official sources: state agencies, statutes, administrative rules.
Every answer links to the page we read and shows the date we checked it.
If we could not confirm it, we say “Not yet verified” instead of guessing.

What counts as a source

We read the issuing agency's own licensing page, application packet, statute or administrative rule. Trade-association summaries, vendor blogs and forums are used only as leads, and are labeled Lead (unconfirmed) when shown.

What the labels mean

State license required	The state requires a license, certification, permit or registration with competency requirements for this work.
No state trade license – local rules	No statewide trade license was found on an official source. Cities, counties or fire districts may license the work, and a general contractor registration may still apply.
Not yet verified	We have not yet confirmed the rule on an official source. It does not mean no license is needed. These pages are kept out of search results until verified.

Blank fields

“Not stated in the source we checked” means the source did not cover that detail (for example fees or CE). It does not mean there is no requirement.

Keeping it current

Every source URL is re-fetched weekly. The text is normalized and hashed. When a page changes, or returns an error, it is flagged for human review, and status changes are published on What changed. Each answer shows its own check date. The full list is on Official sources.

Coverage today

Fire sprinkler and fire alarm: 89 of 102 state answers verified.
ITM and special hazards suppression: 30 of 102 verified (partially verified trades).
Adopted NFPA editions: 2 states verified so far.

Not legal advice

Summaries are plain-English restatements of official sources. Always confirm with the issuing agency and the local AHJ before bidding or performing work.