Requirement 1 — Written by a qualified, observant sofer
A kosher mezuzah must be handwritten by a qualified sofer — a trained, G-d-fearing scribe who is shomer Torah u'mitzvos. The text of the two Torah passages (Shema and V'haya im shamoa) is inscribed by hand, letter by letter, with a quill and kosher ink. This is non-negotiable: a printed, photocopied, or machine-produced scroll is pasul (invalid), no matter how perfect it looks. The mitzvah lives in the act of writing, not in the appearance of the letters.
The sofer's competence and personal observance matter because so much of a scroll's validity depends on things you cannot see after the fact — the order of writing and the intention behind each holy Name. A scroll written by an unqualified or non-observant scribe cannot be relied upon. This is why a kosher mezuzah is best identified by a named sofer rather than by its look.
Requirement 2 — Kosher klaf in a recognized ksav
The passages must be written on kosher klaf — parchment prepared from the hide of a kosher animal and processed lishmah (for the sake of the mitzvah). Paper, synthetic sheets, or improperly prepared parchment invalidate the scroll.
The lettering must follow a recognized ksav (script). Three accepted traditions are Ksav Beis Yosef (used generally by Ashkenazim), Ksav Arizal / Ari (the chassidic script), and Ksav Vellish / Sefardi (used by Sephardim). The right choice is the one that matches your family's mesorah: Ashkenazim generally use Beis Yosef, chassidim use Arizal, and Sephardim use Vellish. Matching the scroll's ksav to your tradition is part of a properly chosen mezuzah; the precise application is a question for your rav or sofer.
Requirement 3 — Tzurat ha'ot, lishma, and kesidran
Every letter must have its correct form — tzurat ha'ot. A letter that is malformed, broken where it should be whole, joined to a neighbor where it should be separate, or otherwise unrecognizable can invalidate the scroll. There can be no missing letters and no extra letters, and letters that should be distinct may not touch.
Two further conditions govern how the writing happens. The scroll must be written lishma — with proper intention, for the sake of the mitzvah, with special concentration when writing the Names of Hashem. And it must be written kesidran — strictly in order, from the first word to the last. If a word or letter was skipped and filled in afterward, the scroll is pasul even though nothing looks wrong. Because lishma and kesidran are invisible on the finished klaf, they trace back to the trustworthiness of the sofer and the verification that follows.
Requirement 4 — Checked after writing by a trained magiah
After the writing is finished, the scroll must be checked by a trained magiah — a proofreader expert in the laws of safrus. The magiah verifies that every letter is correctly formed, that nothing is missing, extra, or touching, and that the text is complete and accurate. Today this check is often supported by computer scanning, but a knowledgeable human magiah remains essential. A scroll that has not been properly checked should not be assumed kosher.
This is also why a sealed scroll cannot be judged by sight, and why ongoing checking matters. A private home's mezuzah is checked twice every seven years, and a communal or public one twice in fifty years — a halacha codified in Shulchan Aruch, Yoreh De'ah 291:1, drawn from the baraisa in the Gemara, Yoma 11a. ("Shavua" there means the seven-year shemittah cycle, not a week.) Beyond that schedule, check immediately after exposure to heat, cold, or moisture; case damage; fire or flood; or any fading or cracking of the ink — and outdoor mezuzos are commonly checked more often. Sight alone is never sufficient.
How to actually verify a scroll — by source, not by appearance
You cannot confirm a kosher mezuzah by looking at it. The fonts that make a scroll valid or invalid are subtle, and the decisive factors — lishma, kesidran, kosher klaf — are invisible on a finished scroll. Verification therefore runs through the scroll's source: the named sofer who wrote it, the named magiah who checked it, the ksav it is written in, a recognized certification such as the Orthodox Union (OU), and clear traceability back to your specific scroll.
As a worked example of what that traceability looks like in practice, Kosher Mezuzah (Stam Mehudar Co., 40+ years) sells OU-certified scrolls handwritten in Eretz Yisrael, each QR-traceable to the individual sofer and magiah, in Ashkenaz, Sefardi, and Arizal scripts. The structure is the point: a verifiable chain from a named scribe and checker, in a stated ksav, under recognized certification — which is exactly what "kosher" depends on. For any specific halachic question about your own scroll, your rav is the final word.
Common questions
- What makes a mezuzah scroll kosher?
- Four things together: it must be handwritten by a qualified, observant sofer (printed or photocopied scrolls are invalid); written on kosher klaf in a recognized ksav such as Beit Yosef, Arizal, or Vellish; have every letter properly formed (tzurat ha'ot), written in order (kesidran) and with proper intention (lishma), with no missing, extra, or touching letters; and be checked after writing by a trained magiah. If any one fails, the scroll can be pasul. For your specific situation, ask a rav.
- Can you tell if a mezuzah is kosher just by looking at it?
- No. A sealed scroll can't be judged by sight, and even an open one hides the decisive factors — whether it was written lishma (with proper intention), kesidran (in order), and on truly kosher klaf. The letter forms that invalidate a scroll are subtle. Real verification runs through the source: a named sofer, a named magiah, the stated ksav, a recognized certification like the OU, and traceability to your specific scroll.
- 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 — ruled in Shulchan Aruch, Yoreh De'ah 291:1, based on the baraisa in Gemara Yoma 11a. ("Shavua" means the seven-year shemittah cycle, not a week.) Check immediately, too, after exposure to heat, cold, or moisture, case damage, fire or flood, or any fading or cracking of the ink. Outdoor mezuzos are commonly checked more often; sight alone is never enough.
- Does the mezuzah case have to be kosher?
- No. The case is decorative and halachically optional — it protects and adorns the scroll but is not the mitzvah. The mitzvah is the handwritten klaf inside. A beautiful case on a non-kosher or unchecked scroll is still not a kosher mezuzah, and because a sealed scroll can't be judged by sight, the case tells you nothing about validity. Focus on the scroll's source and verification, and consult a rav for any specific question.