How the company index is built

Scope and inclusion

The index covers companies with an identifiable, active UK commercial presence and meaningful semiconductor activity: chip design, semiconductor intellectual property, wafer fabrication, compound semiconductors, photonics, power devices, packaging and test, production equipment, materials, and closely related specialist services.

A company is considered only when that activity can be evidenced from a first-party source — normally the company's own website, a Companies House filing, or an official programme, cluster or research-institution record. Records that cannot meet this standard are held for further research or excluded; they are never published speculatively.

Pure distributors, resellers and companies whose semiconductor involvement is incidental are excluded. Early-stage companies are not excluded for being young where first-party operating evidence of genuine semiconductor activity exists.

Classification

Every published record is classified as dedicated or diversified. Dedicated means semiconductors are the core business. Diversified means meaningful semiconductor design or manufacturing capability sits alongside other activity. Where a case is genuinely uncertain, the record is classified conservatively as diversified.

Each genuinely distinct operating business is counted once. Where a company has been acquired and now trades as part of its new owner, the two are held as a single record rather than counted separately. UK operating location, headquarters status and parent ownership are treated as different things: an international group with a real UK engineering or manufacturing operation can be included, and the record describes the UK activity rather than the group as a whole.

Classification is editorial judgement and will sometimes be arguable, particularly for groups spanning several businesses. Individual classification decisions are revisited when new first-party evidence emerges.

Sources and confidence

Each record carries the source used to verify it and the date it was last checked. These details are held privately and used when records are re-verified; they are not displayed on the public page.

Sources are ranked by confidence. The company's own current website and Companies House filings rank highest; official Government, programme and research-institution records follow. Records resting on weaker or indirect evidence are flagged internally for re-checking and are strengthened or removed at the next review rather than left standing unchallenged.

Sector-wide counts and composition figures quoted elsewhere on this site come from the 2026 UK Government Semiconductor Sector Study, which describes them as experimental estimates. The index itself is independently compiled and verified record by record, and deliberately differs from that study: it counts published, individually verified companies, not an estimate of the whole sector.

Review cycles

Records are re-verified in rolling cycles rather than all at once. Each review confirms the company still operates, still has semiconductor activity, still trades under the recorded name, and that its website and classification remain accurate. The internal last-checked date is updated at each pass.

Out-of-cycle reviews are triggered by reader corrections, announced acquisitions, renamings and closures, and by re-check flags raised at earlier reviews. Records that fail re-verification are corrected, held for further research, or removed.

Taxonomy — the controlled lists of capabilities, technologies and regional clusters used to organise the index — is itself reviewed periodically so that labels stay consistent as the index grows.

Currency and limitations

The index is partial by design: records are added only when they can be verified, so it is published short rather than padded. It will always lag company formations, acquisitions, renamings and closures, and counts shown anywhere on this site are counts of published records on that day, not an estimate of the size of the UK sector.

Substantive reviews of this methodology and of the index content are recorded in page metadata rather than as visible dates, so that search and AI tools can use them without implying a precision the record-by-record review cycle does not have.

Independence

Inclusion cannot be bought, and no commercial relationship — partnership, announcement, event or appointment — affects whether a company appears in the index, how it is described, or where it sits in the list. Commercial activity on this site is kept separate and is described in the commercial policy.

If a record is wrong or out of date, or a company with UK semiconductor activity is missing, corrections and suggestions are welcome through the form on the index page. Supporting first-party sources are especially helpful. Corrections are free and are never conditional on any commercial relationship.