Anonymize my ID

How to redact a passport or ID card (and what to hide)

Exactly which fields to cover, which to keep, and how to do it in a minute.

By David Pelayo · · Updated August 1, 2026 · 3 min read

Short answer

Cover the fields a stranger could use to be you, and keep only the fields that prove you are you to the person asking. In practice: solid boxes over the document number and the machine-readable zone, plus your date and place of birth and your signature — then flatten the image and add a watermark.
  • Use solid bars, not blur — blur and light pixelation can sometimes be reversed.
  • Do not skip the machine-readable zone: it re-encodes the number and date of birth, so hiding the printed number alone is not enough.
  • Flatten the export so there is no editable layer left to peel back.
  • When in doubt, hide it — a second, less-redacted copy is easy; clawing one back is not.

Redacting a document sounds technical, but it comes down to one idea: cover the fields a stranger could use to be you, and keep only the fields that prove you are you to the person asking. Get that split right and a copy of your passport or ID becomes almost useless to a fraudster while still doing its job.

Which fields to hide on a passport data pageSchematic of a passport data page. The photo, surname, given names and nationality are marked keep-visible; the document number, date of birth, expiry date, place of birth, signature and the two machine-readable zone lines across the foot of the page are marked hide.PASSPORT / DATA PAGEPhotoSurnameGiven namesDocument numberNationalityDate of birthDate of expirySignaturePlace of birthMachine-readable zone (MRZ)
  • Cover before sharing
  • Usually safe to leave visible
A passport data page, field by field. The same split applies to an ID card — only the layout changes.

What to hide

These are the fields that do the damage if they leak. Cover every one of them:

  • The document number — passport number, DNI/NIE number, or ID card number.
  • The machine-readable zone (MRZ) — the two lines of <<< characters at the bottom of a passport, or the code block on the back of an ID card. Its layout is fixed by ICAO Document 9303, a public standard, so anything that can read one passport can read yours. It re-encodes the number, your date of birth and expiry, so hiding the number alone is not enough.
  • Date and place of birth.
  • Your signature.
  • The support / CAN number on the back of many national ID cards, and any parents’ names printed there.
  • Issue and expiry dates, unless the recipient specifically needs to confirm validity.

What you can usually keep

Leave visible only what the recipient must actually match:

  • Your name.
  • Your photo — so a hotel or rental desk can match your face to the booking.
  • Nationality, where it is relevant to what they are checking.

When in doubt, hide it. It is far easier to send a second, less-redacted copy than to claw back one that showed too much.

A note on blur versus solid bars

Not all redaction is equal. A solid bar removes the pixels entirely and cannot be reversed. Heavy blur or light pixelation can, in some cases, be undone by software: researchers at Cornell Tech and UT Austin showed in Defeating Image Obfuscation with Deep Learning that a neural network can read faces, objects and digits back out of both mosaiced and blurred images. Keep those techniques for low-stakes areas and use solid bars over the number and MRZ. Whatever you use, flatten the result into a new image; never send an editable file with removable layers on top.

The steps below walk through the whole process. Anonymize my ID does each one on your phone, offline, in about a minute — but the sequence is the same whichever tool you use.

Redact a passport or ID, step by step

  1. Start from a clear photo, offline. Photograph the document on a plain background in good light, or pick an existing photo. Use an app that works entirely on your device so the image is never uploaded.
  2. Cover the number and the machine-readable zone. Place solid boxes over the document number and the two code lines at the bottom. These two fields are what most document fraud relies on.
  3. Hide your date of birth and signature. Add your date of birth and handwritten signature to the redaction. Leave your name and photo visible only if the recipient must match them.
  4. Use partial redaction where it helps. If someone needs to confirm only the last few digits of a number, reveal those and hide the rest.
  5. Add a watermark tied to the recipient. Write who the copy is for and the date across the whole image, tiled so it cannot be cropped out — for example, 'For visa application, 30 June 2026'.
  6. Export the redacted copy — and only that. Save or share the redacted, watermarked version, never the original, and delete the copy once it has done its job.

Frequently asked questions

What should I never leave visible on an ID copy?

The document number and the machine-readable zone. Together they are the keys to most document fraud. Hide your date of birth and signature as well.

Is a solid box safer than blur?

Yes. A solid bar cannot be undone, whereas heavy blur or light pixelation can sometimes be reversed. Use a solid bar for numbers and the machine-readable zone; blur is fine for less critical areas.

Can I redact a passport for free?

Yes. Anonymize my ID includes free anonymizations that hide every field in black and white with a watermark. A one-time Pro unlock adds full control over what to hide and how.