es_dni

Spanish ID card (DNI)

Check that a Spanish DNI is valid, not expired and belongs to the right person.

Category: Identity
Country: Spain
Extracted fields: 14 fields
Cost: 1 credit

es_dnispecimen

Document number
First name
First surname
Second surname
Sex
Nationality
Date of birth
Expiry date
Issue date

The DNI is the most requested document in Spain, and the one most often stored for no reason. Constaia reads both sides, computes the check letter, validates the MRZ and compares it with the printed data. You get a verdict with reasons and, if you want, only the minimum fields.

A photo of each side, or one PDF with both, counts as 1 credit.
With storage "none" the file is deleted as soon as the analysis ends: you never keep a copy of the ID.
A correct letter and MRZ do not prove the document is authentic; warnings flag screen photos or possible edits.

What it checks

NIF/NIE check letter. The check character is recomputed (mod 23).
MRZ ICAO 9303. Check digits of the machine readable zone.
MRZ vs printed data. The MRZ matches the visible data.
Validity. Not expired on the reference date.
Holder. Name, number or date of birth match what you expect.
Age. Minimum or maximum age from the date of birth.

Extracted fields

Document numberdocument_number
First namefirst_name
First surnamelast_name_1
Second surnamelast_name_2
Sexsex
Nationalitynationality
Date of birthbirth_date
Expiry dateexpiry_date
Issue dateissue_date
Support numbersupport_number
Addressaddress
Place of birthbirth_place
Parents' namesparents
Mrzmrz

Sample request

curl https://api.constaia.com/v1/analyze \
  -H "Authorization: Bearer $CONSTAIA_API_KEY" \
  -F "file=@dni_valid.jpg" \
  -F 'options={
    "expect": "es_dni",
    "checks": {
      "not_expired": true,
      "holder": {
        "full_name": "María García López"
      }
    },
    "storage": "none"
  }'

Try it for free with a ck_test_ key and the file dni_valid.jpg.

Sample response

Fictitious data. Shortened response.

200 OK · application/json

{
  "id": "an_01J9Z3K8QW4T6Y2B7N5M1R0PXC",
  "object": "analysis",
  "status": "completed",
  "livemode": false,
  "document": {
    "type": "es_dni",
    "label": "Spanish ID card (DNI)",
    "confidence": 0.97
  },
  "verdict": {
    "expected": [
      "es_dni"
    ],
    "match": true,
    "status": "valid",
    "reasons": [
      {
        "code": "type_match",
        "severity": "info",
        "message": "The document is: Spanish ID card (DNI)."
      }
    ]
  },
  "fields": {
    "document_number": {
      "value": "12345678Z",
      "confidence": 0.99,
      "validated": true
    },
    "first_name": {
      "value": "MARÍA",
      "confidence": 0.98,
      "validated": null
    },
    "last_name_1": {
      "value": "GARCÍA",
      "confidence": 0.97,
      "validated": null
    },
    "last_name_2": {
      "value": "LÓPEZ",
      "confidence": 0.96,
      "validated": null
    },
    "sex": {
      "value": "F",
      "confidence": 0.99,
      "validated": null
    },
    "nationality": {
      "value": "ESP",
      "confidence": 0.98,
      "validated": null
    },
    "birth_date": {
      "value": "1990-04-18",
      "confidence": 0.97,
      "validated": null
    },
    "expiry_date": {
      "value": "2031-03-12",
      "confidence": 0.96,
      "validated": null
    }
  },
  "checks": [
    {
      "code": "nif_check_digit",
      "passed": true,
      "message": "The NIF check letter is correct."
    },
    {
      "code": "mrz_checksums",
      "passed": true,
      "message": "The MRZ check digits are correct."
    },
    {
      "code": "mrz_matches_visual",
      "passed": true,
      "message": "The MRZ matches the printed data."
    }
  ],
  "warnings": [],
  "storage": {
    "mode": "none",
    "file_deleted_at": "2026-09-29T10:00:02Z",
    "expires_at": null
  },
  "usage": {
    "credits": 1,
    "pages": 2
  }
}

FAQ

Does Constaia prove the document is authentic?

No. It checks the type, data consistency and your rules, and flags signals such as a possible edit or a screen photo. That does not prove authenticity.

Is a copy of the document kept?

No, unless you ask for it. With storage "none" (the default) the file is deleted when the analysis ends.

And for the record…

Create your account, copy the test key and validate your first document in five minutes.

Create a free account Talk to sales