How we verify

London Mempool is a free map of the best tech companies in London. It lists 759 companies, and 758 of them are matched to a UK Companies House record. Anyone can check any fact on it.

What we check

• Legal entity. The company number and status on Companies House, linked on every card.
• London office. A real address with a source. The pin comes from the postcode, using official ONS data from postcodes.io.
• Funding. Total raised and the latest round, each linked to a press release or credible report.
• Growth. One fact that backs up the group it sits in, with a source.

Every company gets two separate checks. The second one tries to prove the first one wrong. If a fact can't be sourced, we leave it out. If a company can't be verified, it doesn't go on the map.

Hiring and visas

• Hiring. We find each company's public job board (Ashby, Greenhouse, Lever, Workable, Teamtailor or Personio) and count the open roles based in London. 191 companies have at least one. Each card shows the date we checked.
• Visa sponsors. We match each company to the Home Office register of licensed Worker sponsors. We only accept an exact match on the legal name, or on the trading name when the sponsor is in London. 597 companies are on it.

A missing flag means we didn't find it, not "no". The company may use a job board we can't read, or sponsor under a different name.

Work model

On-site, hybrid or remote comes from the same public job boards, and only from the company's current London job posts. We use the board's own workplace field (Ashby, Lever, Workable, Teamtailor) or a location that literally says Hybrid, Remote or On-site (Greenhouse, Personio). We never read the job description. When 80% or more of the London posts that state a type share one, that is the work model; otherwise it is mixed. Fewer than two typed posts and we leave it blank. 119 companies have one (66 hybrid, 25 on-site, 6 remote, 22 mixed).

It reflects current job posts only. It is not the company's policy, and it changes as roles open and close. A blank means the posts don't say, not that there is no office.

Sectors

Every company has one main sector. That is the colour of its pin, and it is the only sector used in totals, so the sector counts on the map, the stats page and the API add up to the number of companies.

Some companies clearly sit in two places, like an AI lab that designs drugs, a regulated crypto exchange, or a defence company whose product is AI. They get a second sector. 82 of 759 companies have one. We assign it by hand from the company's own description, and only when the overlap is clear. When in doubt, there is none, and Other is never a second sector.

A company shows on both sector pages. On its second one it sits in an "Also in" group with a small marker, and is not counted in that sector's total. The sector filter on the map and in the API matches either sector, and the map chips show it as two numbers, e.g. AI 177+35: 177 with AI as the main sector, plus 35 with it as the second. The downloadable landscape PNG shows main sectors only, to keep it clean. Agents can pass primary_only=true to match the main sector only.

London presence

Some companies are run from London. Others have a London office or just a London team. Where we have checked, each company gets one of three values, backed by a source link:

• London HQ. The main or global headquarters is in London.
• London office. A London office, with the headquarters in another city.
• Team only. Staff based in London, but no London office.

We check the Companies House registered office, the careers page and the company's own site. On the map an HQ is a solid pin, an office is a ring and a team with no office is a faded pin. A company with no value has not been checked yet. That doesn't mean it has no London base. 756 companies are checked so far.

Companies House dates and SIC codes

• Incorporated on. The date the legal entity was created, read from the company's page on the public Companies House register. 743 of 759 companies have one. It can be later than the year founded, for example when a company moved its legal entity to the UK. A UK branch of a foreign company shows an opening date, not an incorporation date, so we leave it blank.
• SIC codes. The nature of business the company gives Companies House, as standard industry codes (SIC 2007). 741 companies list at least one. Companies pick their own codes, so they show how a company files, not what it builds.

We read each page as it is and never fill gaps by hand. The headline numbers on London tech in numbers count only companies listed on London Mempool, so they describe this map, not all of London. Ages are whole years from the incorporation date. "Since 2023" means incorporated on or after 1 January 2023, three calendar years before the year of the figures.

Staff from filed accounts

UK companies must state the average number of people they employed during the year in their annual accounts. "Staff (Companies House accounts)" is that figure from the latest accounts each company filed, for the period the accounts are made up to, with a link to the filing. We read it only from accounts filed in iXBRL, where the number is tagged, for the current period. Group accounts can give two numbers: the registered company's own staff and the whole group's. We take the company's own figure when it is there, and label it "across the group" (4 companies) when the accounts give only the group figure, which can include staff of subsidiaries outside the UK. Some filing software tags the number as if it were a percentage (a printed 59 tagged as 0.59); there we use the number printed in the accounts.

340 of 758 companies with a Companies House number have a figure. A blank means we could not read one, not that the company is small: most large companies file their full accounts as a PDF only, which we do not read. We also leave it blank for dormant accounts, UK branches of overseas companies, accounts that report no employees or a fraction, group accounts that tag a single number without saying whether it is the group's or the company's, and any filing where the figure is unclear, for example two different numbers for the same period or a number that cannot be a headcount.

Read it as a past figure, not today's headcount. It is an average over a period that has already ended, and accounts are filed up to nine months after that, so a company that is growing fast is usually bigger now. When the London company is a subsidiary of a larger group, the figure covers only the staff that entity employs, so it can undercount the whole team. It sits next to the reported team size; it does not change that bucket or the tiers. Filter with min_staff in the API.

Nearest station

Each company gets the closest Underground, Elizabeth line, DLR or Overground station to its office postcode, using station locations from TfL open data. The distance is a straight line, so the walk is a little longer. National Rail only stations are not included. See them all on the Tube map.

Investors

For each company we fetch its funding announcements and record the institutional investors a page names: venture firms, corporate venture arms, growth funds and public funds like British Business Bank. Angels, grants and lenders are left out. An investor is marked as lead only when the page says it led a round. Every name links to the page that names it, and anything without a source is dropped.

Names are tidied so one firm counts once: legal endings like LLP or Limited are dropped, and old names map to the current one (Draper Esprit is Molten Ventures). A fund and its parent stay apart, so Coinbase and Coinbase Ventures are two entries. 660 of 759 companies have at least one sourced investor so far.

The investor leaderboard ranks investors by how many companies on the map they back. It needs 2 or more to rank, and investors with the same count share a rank. 430 investors are ranked. Because we only count what a source names, every number is a floor, not a full cap table. A missing investor means we didn't find a page that names it, not that it didn't invest.

Funding rounds

Each company's last round is a line of text from its sourced funding record, such as "Series A, $30M, Jun 2026". It is the most recent round we have on record, not a full history. 567 of 759 companies have one.

From that text alone, a small parser reads four things, and leaves each one blank when the text is unclear. The month, only when the text names exactly one month and year (533 companies). The stage, normalised to Pre-seed, Seed, Series A to H, Growth, IPO, Grant, Debt or Other: Series A2 and A+ count as Series A, a round that names two stages gets the later one, and Pre-Series A counts as Seed (559). The kind: debt when the text names only debt, a facility, a loan or credit; mixed when it names more than one kind, such as equity and debt; grant for a grant alone; equity otherwise. A convertible note, a bridge or a refinancing is left blank, because the text does not say which it was (548 with a kind). The amount, only when the text names exactly one exact figure (520): a currency conversion like £9.5M ($12M), a floor like $80M+ or an approximate figure is left blank, and a valuation is never an amount. Acquisitions and secondary share sales are not rounds, so all four stay blank.

The recent rounds page lists every last round dated in the 12 months up to the data date, grouped by month, with the amount as written and a link to the source. An equity round there, and in the raised_since filter, is one whose kind is equity or mixed.

Context layers

The map can show 55 places that help you read it: VC offices, big tech offices, universities, accelerators and coworking spaces. They are landmarks, not companies on the list, and they are not ranked. They are off by default and drawn in grey. Turn them on with the Layers button on the map.

• VCs31
• Big tech7
• Universities7
• Accelerators2
• Coworking8

Every place links to a page we fetched that shows its London address, often the firm's own contact or privacy page, or its Companies House record. The pin comes from the postcode. If we couldn't find a page that shows a London address, the place isn't here, even if it is well known. The Tube lines layer joins each pair of neighbouring stations from TfL open data with a straight line, so it is a guide, not a track map. All places are in places.json.

Logos

The logo grids on each sector page (for example the AI landscape) use one logo per company, fetched from the company's own website: its app icon first, then a large site icon, then its favicon if it is at least 64 pixels. We only take an image that the company's own page links to, on its own domain or the content network its page loads files from. Nothing is drawn or guessed: a company without a usable logo gets a tile with its initials in the sector colour. 611 of 759 companies have a fetched logo.

Logos and trademarks belong to their owners. They are shown only to identify each company. If you run one of these companies and want your logo changed or removed, tell us.

GitHub

A company's GitHub organisation is taken only from a link on its own home page, fetched on its own domain (a page that redirects to another domain is skipped). We ignore links to GitHub's own pages and links to other people's projects, such as a theme or library credit, and we keep an account only when it clearly belongs to the company: the public GitHub API lists it as an organisation whose name matches the company or its domain, or the account itself shows the company's website. When a page links several unrelated accounts we leave it blank. 50 of 759 companies have one. A blank does not mean a company publishes no open source, only that its home page does not link an account. Filter with open_source=true in the API.

Accelerators

Accelerator programmes come only from each programme's own public list, matched by the company's website domain, never by name alone. The name is used only to confirm a domain match. For Y Combinator we read the public directory and record the batch as YC writes it (W24 is Winter 2024, S for Summer, F for Fall, X for Spring); each match links to the company's page on ycombinator.com, and we load that page to check it shows the batch and the company's website. A YC company in the UK whose listed website now redirects to the company's current domain also counts. Antler, Founders Factory and Conception X publish portfolio pages that link each company's website, so a link to the company's domain, with its name next to it, counts; Conception X cohorts (CX24) come from the same card. Programmes that publish no list of company websites, such as Entrepreneur First and Techstars, are not covered, and we do not read anything behind a login. 55 of 759 companies have one (Y Combinator 41, Antler 6, Founders Factory 5, Conception X 4). A blank does not mean a company never did an accelerator. Filter with accelerator=y-combinator in the API.

Recognition lists

"Recognised on" lists published, named rankings and cohorts that include a company, each read from the publisher's own page or PDF: the Sifted 100 UK & Ireland (2024 and 2026 PDFs), Tech Nation's Future Fifty and Upscale cohort announcements (2024 to 2026), the Deloitte UK Technology Fast 50 winners tables (2023 to 2025), LinkedIn Top Startups UK (2023 to 2025) and the Forbes AI 50 (2024 to 2026). A company counts when the list links its website or LinkedIn page, or when the list shows its exact name (or exact Companies House name) with a London or UK location, or the list only takes UK companies, and nothing on the list contradicts us: no different website, LinkedIn page or founding year. A website that has since moved counts when the list's link now redirects to the company's domain. Anything close but not certain is left out and kept for review. Ranks are shown only for ranked lists; Tech Nation cohorts and the Forbes AI 50 are unranked. Lists we could not fetch or parse (FT 1000, Sunday Times 100, CB Insights AI 100, Sifted 100 UK & Ireland 2025, which sits behind a login) are not covered. 215 of 759 companies are on at least one (Sifted 100 UK & Ireland 118, Tech Nation Future Fifty 67, Tech Nation Upscale 24, Deloitte UK Technology Fast 50 62, LinkedIn Top Startups UK 32, Forbes AI 50 3). Filter with cohort=sifted-100-uk-ireland in the API.

Blockchain ecosystems

"Builds on" applies to crypto companies only (primary or secondary sector). It names the blockchain a company's product is built on or primarily supports, and only when the company's own site, docs, GitHub or announcement says so; each chain links to that page. Names are normalised to a fixed list (Ethereum, Bitcoin, Solana, XRP Ledger, Tezos, Starknet and others). A protocol deployed on many chains gets only the chain it names first or as its home. Exchanges, custodians, brokers, market makers, payment rails, benchmarks and analytics providers that support many assets are left blank, as are companies whose own pages name no chain, so a blank is not a claim that a company uses none. 5 of 35 crypto companies have one (Ethereum 3, Tezos 1, Starknet 1, Plasma 1). See them by chain, or filter with ecosystem=ethereum in the API.

Notes

The notes are short pieces on patterns in this data. Every number in them is computed from the dataset each time the site is built, so a note always matches the data on the date it shows. Only the titles and the method lines are written by hand. They say where and how many, not why. Neighbourhoods come from each office postcode and hand-drawn boundaries; anything outside them is Elsewhere in London, which is never ranked as a neighbourhood. Sectors are the primary sector only, and Other, the catch-all, is left out of sector comparisons. Small groups are left out too: a note says the minimum it uses.

Corrections and additions

Spotted something wrong, or a company that should be here? Send it with a source and we'll check it. Running a London tech company yourself? Add your company with its Companies House number and get a status page.

Use the data

The full dataset is free, sources included. Download the CSV.