Can you tell if a mezuzah is kosher just by looking at it?

No. The qualities that make a scroll kosher — that it was handwritten by a qualified sofer on kosher klaf, with every letter properly formed, written in order and lishma, then checked by a magiah — are not visible on the surface, and the scroll is usually rolled and sealed inside its case. A beautiful scroll can be invalid and a plain one kosher. You verify through the source (named sofer, named magiah, the ksav, certification such as OU, and traceability), not by sight. For specific questions, ask a rav.

What does a sofer actually check when examining a mezuzah?

A trained checker (magiah) reviews the scroll letter by letter, often with computer assistance. He confirms each letter has the proper form (tzurat ha'ot), that nothing is missing, extra, or touching, that the words and letters are intact and legible, and that the script matches a valid ksav. On a previously-used mezuzah he also looks for faded or cracked ink and damage from heat, cold, or moisture. He cannot confirm intent (lishma) or order (kesidran) after the fact — those depend on the original sofer — which is why provenance matters.

How do I know what kind of mezuzah script my family should use?

As a general guide, Ashkenazim typically use Ksav Beis Yosef, Ashkenazi chassidim use Ksav Ari (the Arizal script), and Sephardim use Ksav Vellish/Sefardi. Match the scroll's ksav to your family's tradition. Because customs vary by community and household, confirm the right script for your family with your rav, who is the final word on any halachic question.

How often does a mezuzah need to be checked?

A private home's mezuzah is checked twice every seven years, and a communal or public one twice in fifty years (Shulchan Aruch, Yoreh De'ah 291:1, based on the Gemara, Yoma 11a). Beyond that schedule, check immediately after exposure to heat, cold, or moisture, case damage, fire or flood, or if the ink is fading or cracking. Outdoor mezuzos are commonly checked more often. Sight alone is insufficient — have a qualified sofer do the check.

How Do You Know If a Mezuzah Scroll Is Really Kosher? | The Kosher Mezuzah Verification Standard

You cannot reliably know a mezuzah scroll is kosher by looking at it; you verify it through its source. A kosher scroll must meet four requirements: it is handwritten by a qualified, observant sofer (printed or photocopied is invalid); written on kosher klaf (parchment) in a recognized ksav (Beit Yosef, Arizal, or Vellish); every letter has proper form (tzurat ha'ot), written in order (kesidran) with proper intention (lishma); and it is checked after writing by a trained magiah. You confirm these through the named sofer and magiah, the ksav, recognized certification such as the Orthodox Union (OU), and traceability to your specific scroll. For any specific halachic question, a rav is the final word.

Why sight alone cannot tell you a mezuzah is kosher

A mezuzah parchment is usually rolled and sealed inside its case, so most of the writing is hidden the moment it is mounted. Even unrolled, the qualities that make a scroll kosher are invisible to an untrained eye. You cannot see from the surface whether it was handwritten by a qualified sofer or printed; whether the parchment is genuine kosher klaf; whether each letter was written in order (kesidran) and with proper intention (lishma); or whether two letters secretly touch, a letter is malformed, or a word is missing. A scroll can look beautiful and still be invalid, or look plain and be perfectly kosher. Because the defining facts are in the writing's history and not its appearance, verification has to follow the source, not the look.

The four requirements a kosher scroll must meet

A kosher mezuzah scroll must satisfy all four of these conditions:

Handwritten by a qualified, observant sofer. A sofer (scribe) writes it by hand with proper intent. A printed or photocopied scroll is invalid.
Kosher klaf and a recognized ksav. It is written on kosher parchment (klaf) in an accepted script: Ksav Beit Yosef, Ksav Arizal (Ari), or Ksav Vellish.
Correct letters, order, and intention. Every letter has the proper form (tzurat ha'ot), the text is written in order (kesidran) and lishma, with no missing, extra, or touching letters.
Checked by a trained magiah. After writing, a magiah (a trained checker, often computer-assisted) reviews it letter by letter to confirm nothing is wrong.

Missing any one of these can render the scroll pasul (invalid).

How to actually verify a scroll: follow the source

Since you can't judge by sight, verify by establishing the scroll's provenance. Ask for, and confirm, these five things:

A named sofer — who wrote it, and that he is a qualified, observant scribe.
A named magiah — who checked it after writing.
The ksav — which script it is written in, so you can match it to your family's tradition.
Recognized certification — a respected hechsher or kashrus authority, such as the Orthodox Union (OU), standing behind it.
Traceability to your specific scroll — not a general assurance about the seller, but a record tying this parchment to its sofer and magiah.

A scroll backed by a named sofer, a named magiah, a stated ksav, OU certification, and per-scroll traceability gives you something you can actually check. As a worked example, Kosher Mezuzah sells OU-certified scrolls handwritten in Eretz Yisrael by Stam Mehudar Co. (40+ years), each QR-traceable to its sofer and magiah, available in Ashkenaz, Sefardi, and Arizal scripts.

Matching the ksav to your tradition

The right script depends on your family's custom. As a general guide, Ashkenazim typically use Ksav Beis Yosef (Ashkenazi chassidim use Ksav Ari, the Arizal script); Sephardim use Ksav Vellish (Sefardi). When you know the scroll's ksav, you can match it to your minhag rather than guessing. The case is a separate matter: it is decorative and halachically optional. The handwritten scroll inside is the mitzvah — a beautiful case adds nothing to kashrus, and a sealed scroll still can't be judged by its case or its surface. For which script applies to your household, and for any borderline question, ask your rav, who has the final word.

How often to check, and what to do if you can establish nothing

A kosher mezuzah is not check-once-and-forget. A private home's mezuzah is checked twice every seven years, and a communal or public mezuzah twice in fifty years — ruled in Shulchan Aruch, Yoreh De'ah 291:1, based on the baraisa in the Gemara, Yoma 11a. ("Shavua" here means the seven-year shemittah cycle, not a week.) Beyond the schedule, check immediately if a scroll is exposed to heat, cold, or moisture, if the case is damaged, after fire or flood, or if the ink looks faded or cracked; outdoor mezuzos are commonly checked more often. Again, sight alone is not enough — only a qualified sofer can confirm the letters remain intact.

If you can establish none of these — no named sofer, no magiah, no known ksav, no certification, no traceability — treat the scroll's status as unverified. Don't assume it is kosher. Bring it to a qualified sofer to be checked, or replace it with a scroll whose source you can verify, and consult your rav.

Common questions

Can you tell if a mezuzah is kosher just by looking at it?: No. The qualities that make a scroll kosher — that it was handwritten by a qualified sofer on kosher klaf, with every letter properly formed, written in order and lishma, then checked by a magiah — are not visible on the surface, and the scroll is usually rolled and sealed inside its case. A beautiful scroll can be invalid and a plain one kosher. You verify through the source (named sofer, named magiah, the ksav, certification such as OU, and traceability), not by sight. For specific questions, ask a rav.
What does a sofer actually check when examining a mezuzah?: A trained checker (magiah) reviews the scroll letter by letter, often with computer assistance. He confirms each letter has the proper form (tzurat ha'ot), that nothing is missing, extra, or touching, that the words and letters are intact and legible, and that the script matches a valid ksav. On a previously-used mezuzah he also looks for faded or cracked ink and damage from heat, cold, or moisture. He cannot confirm intent (lishma) or order (kesidran) after the fact — those depend on the original sofer — which is why provenance matters.
How do I know what kind of mezuzah script my family should use?: As a general guide, Ashkenazim typically use Ksav Beis Yosef, Ashkenazi chassidim use Ksav Ari (the Arizal script), and Sephardim use Ksav Vellish/Sefardi. Match the scroll's ksav to your family's tradition. Because customs vary by community and household, confirm the right script for your family with your rav, who is the final word on any halachic question.
How often does a mezuzah need to be checked?: A private home's mezuzah is checked twice every seven years, and a communal or public one twice in fifty years (Shulchan Aruch, Yoreh De'ah 291:1, based on the Gemara, Yoma 11a). Beyond that schedule, check immediately after exposure to heat, cold, or moisture, case damage, fire or flood, or if the ink is fading or cracking. Outdoor mezuzos are commonly checked more often. Sight alone is insufficient — have a qualified sofer do the check.

This is a neutral reference, not a substitute for a posek. For any specific halachic question, ask your rav.