One seal, read by many people.

• What you get: the artist's own word that this is their work, attached to the work itself. It goes with the work when you resell it, lend it or leave it to your family, and anyone can check it with a phone, free.
• What a check proves: the artist (or their gallery or estate) signed that this chip belongs to this work, and the chip answering now is the original. It is not an appraisal: see what “Verified” means.
• Always compare the record and photo with the work in front of you: a seal can be moved to another object.
• Keep a copy: on the result, tap Print or save as PDF and keep it with your invoice. It remains valid even if ArtFirma ever closes (how).
• “Touch the seal again” / “Touch the seal itself”: the page was opened from a reload, a saved link or a screenshot. Touch the seal on the work. If it still does not verify, ask the seller or the artist before relying on it.
• Buying: ask the seller to touch the seal in front of you. Nobody records who checks a work or where.

What a gallery gets: every work you sell carries the artist's own proof. A buyer holds a phone to the seal and sees the artist's name, the work and its photo, at the fair, at home or at resale. One phone, iPhone or Android, about a minute per work. Talk to us →

• Galleries may sign for their artists. Register the gallery's own key, confirmed by the gallery website. The result then reads “Signed by Gallery on behalf of the artist”, with the artist's name as the headline.
• Editions: one seal per print, always, because each seal is bound to its own chip and cannot be copied to another print. The record can be shared: sign as many seals as there are prints from one record (tap Sign seal again for each), or make a record per number (night-field-3-15) when the number must be in the record. Seals are not needed on every print: many artists seal only the more valuable ones.
• Editions already sold with paper certificates can be sealed today: one seal per print, the number in the record; keep the old paper certificate with the work. The seal adds to it; it does not replace it.
• Catalogue wording we suggest: “Accompanied by an ArtFirma seal signed by the artist, verifiable with any NFC phone at purl.org/artfirma.” Please avoid “authenticated by ArtFirma”, since we do not examine works.
• In the saleroom: a buyer who sees Touch the seal itself opened a saved link or screenshot; touching the seal gives a fresh, live reading. Checking many works in a row: open this site in Chrome on Android and tap Check a seal with this phone; each touch is then checked in the same tab.
• If a buyer sees “Not verified”: (1) touch the seal yourself, in front of them, holding it still for a second; (2) if it still shows “Not verified”, withdraw the seal from the description of the sale and write to the artist (or to us) with the printed result; do not argue about the work itself. A neutral phrase: “The seal could not be confirmed today; we are checking it with the artist. The work's other documentation is unaffected.”
• Seals: order them on the order page, in sets of 20, 40, 60, 100 or 500, with free UPS tracked delivery.

How a gallery signs, step by step

1. On the gallery's phone (iPhone or Android), install the ArtFirma app and create the gallery's own twelve words (not the artist's). Keep them like the gallery's safe code.
2. ⚙ → Register as artist: name = the gallery, website = the gallery's site. Put the line it gives on the gallery site (a page artfirma), tap Check & register. No website of your own? Use the gallery's profile page (Artlogic, Instagram) with the line in its text, or write to us.
3. For each work: open its page on the gallery or artist site (or Artlogic) → Share → ArtFirma. Make sure Artist is the artist's name, because that is what the page shows as the headline.
4. Editions: one seal per print. Sign them all from one record (tap Sign seal again for each print), or make a record per number (night-field-3-15, “Night field, 3/15”) when the number must be in the record.
5. Touch the seal to the phone, stick it on the work. About a minute per work; 250 works a year is a few hours in total.

Catalogue wording: when the artist signs, “Accompanied by an ArtFirma seal signed by the artist”; when the gallery signs, “Accompanied by an ArtFirma seal signed by Gallery on behalf of the artist”. Use the one the check page shows.

Works kept in a spreadsheet? The app reads a public web page, so each work needs one simple page on the gallery site (title, year, size, medium, photo), and that page is what you share to the app. No import from Excel.

Auction house? Let's talk →

Keep in your own records, so the evidence survives any outside service:

• the printed or PDF result of a check (it lists all technical details and the date);
• the record file and its signature (<work>.json, <work>.json.sig) and the photo, from the registry or the artist;
• a saved copy of this verification page (one file) and the specification.

Fields worth adding to your collection system: work number, signing key, record fingerprint, chip ID, archive (Arweave) ID, date checked, next to your own accession number. The work number is the artist's; keep both. If the museum signs works itself (with its own registered key), the accession number can be the work number when it uses only letters, digits and dashes: 2026.14.3 → 2026-14-3.

• Seals already signed stay valid forever. Nothing needs to be done for them to keep working.
• Whoever holds the artist's twelve words can carry on the artist's will: sign works the artist left unsigned, update or re-sign seals, and keep the registry and verification available.
• Words lost? No one, including us, can sign with that key again. The estate can register its own key, confirmed by the estate's website (or a public profile page), and sign remaining works; they will read “Signed by Estate on behalf of the artist”.
• To be independent of ArtFirma, the estate can keep its own copy of the records and its own verification page (see run it yourself).
• Write to us and we will help: contact@artfirma.com.

Checklist for the estate

1. Look for the twelve words: a sheet of paper or notebook in the studio, a safe, a sealed envelope with the will. Do not photograph them.
2. Who holds the key is whoever has the words; the system cannot tell an heir from anyone else. Agree within the estate who keeps them, and store them as you would the artist's other valuables.
3. Found: install the app → I already have my 12 words. You can now sign remaining works and re-sign seals in the artist's name.
4. Not found: nothing is lost for the seals already signed. To sign remaining works, create the estate's own words and register them with the estate's website or, without a website, with a public profile page naming the estate (Artlogic, Instagram). You can also write to us. The steps are the same as for a gallery.
5. If the words fall into the wrong hands: revoke the key in the app with ⚙ → Revoke my key, or without the words by putting the line artfirma-revoke=<key> where the key was confirmed (see below).

How to cite a check (example for a condition or appraisal report):

On 7 October 2026 the ArtFirma seal on the work was read with a phone. The verification page reported “Verified · signed”: work number night-field-3-15, signing key b4c6150f… confirmed by ann.example, record fingerprint EcKjHDjAgKLMRSkepwEQYg, chip 04A1B2C3D4E5F6, live chip reading accepted. The record and photo matched the object examined. A printout is attached. This confirms the declaration of the key holder; it is not an attribution.