Standardize Any County Parcel APN
Enter unformatted assessor parcel identifiers to generate canonical keys, spatial regex patterns, and direct county GIS links.
🏛️ Official County Assessor & GIS Map Portals
Complete 3,244 County Assessor & GIS Directory
Search public property portals across all 50 states, District of Columbia, Puerto Rico, Guam, US Virgin Islands, and American Samoa.
| County / Municipality | State | FIPS Code | Assessor / CAD Portal | GIS Interactive Tax Map |
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Developer APN Standardization API
Integrate live parcel standardization and GIS lookup directly into your proptech apps with a high-throughput REST API.
cURL Request
curl -X POST https://apnlookup.org/api/v1/apn/standardize \
-H "Authorization: Bearer apn_live_your_key" \
-H "Content-Type: application/json" \
-d '{
"apn": "045 192 004 0012",
"state": "TX"
}'
JSON Response (200 OK)
10ms{
"raw_apn": "045 192 004 0012",
"clean_digits": "0451920040012",
"canonical_formatted": "045-192-004-0012",
"is_valid_format": true,
"state_jurisdiction": "TX",
"matched_county": {
"county": "Harris County",
"assessor_url": "https://hcad.org",
"gis_url": "https://gis.hcad.org"
}
}
Documentation, Cadastral Standards & APN Lookup FAQ
Technical specification for nationwide Assessor Parcel Number (APN) standardization, FIPS county code mapping, spatial regex formats, and developer REST APIs.
🎯 Cadastral APN Standardization Pipeline & Data Flow
3,244 JURISDICTIONSAcross the United States and territories, 3,244 county assessors use disparate, unstandardized parcel numbering schemas. APNLookup normalizes noisy inputs into canonical hyphenated keys with spatial GIS validation.
🎛️ Complete Widget, Input & Button Encyclopedia
INTERFACE REFERENCE❓ Frequently Asked Questions (FAQ) & Cadastral GIS Guide
16 DETAILED ARTICLES1. What is an Assessor Parcel Number (APN)?
An Assessor's Parcel Number (APN)—also known as a Folio Number, Tax ID, PIN (Property Identification Number), or Map-Block-Lot—is a unique numeric or alphanumeric identifier assigned by a county tax assessor to track real estate parcels for ad valorem taxation.
2. Why are APNs formatted differently across every county?
There is no single federal standard for parcel numbering. Each of the 3,244 US counties designed their own cadastral schemas over the past century (e.g. Map-Block-Lot in New England, Section-Township-Range in the Midwest, Book-Page-Parcel in the West). APNLookup solves this fragmentation.
3. How does the California Book-Page-Parcel APN schema work?
In California, APNs typically follow a 10-digit format: BBB-PP-LLL (e.g. 5412-019-028). The first 3–4 digits denote the Assessor Map Book, the middle 2–3 digits denote the Page, and the trailing 3 digits identify the individual Parcel.
4. How do Texas 13-digit cadastral account numbers operate?
In major Texas counties (like Harris County HCAD and Dallas CAD), APNs use 13-digit structures formatted as 045-192-004-0012, representing District, Subdivision Map Code, Block Number, and Lot Number.
5. How are Florida 13-digit Folio Numbers structured?
Florida folios (e.g. Miami-Dade 01-4138-006-1920) encode Municipality Code (first 2 digits), Section-Township-Range (middle 4 digits), Subdivision/Plat (next 3 digits), and Parcel Sequence (last 4 digits).
6. How does the Puerto Rico (CRIM) Cadastral schema operate?
In Puerto Rico, the Centro de Recaudación de Ingresos Municipales (CRIM) utilizes an 11-digit or 14-digit cadastral key format: 040-028-192-01-000 representing Municipality Code, Map Sheet, Block, and Parcel.
7. How does APNLookup fix the common Excel "Leading Zero" bug?
Spreadsheet software like Microsoft Excel often automatically strips leading zeros from parcel strings (turning 0451920040012 into 451920040012). Our engine detects missing digits based on county cadastral rules and restores leading zeros.
8. What is a FIPS code and how does APNLookup map it to counties?
Federal Information Processing Standard (FIPS) 5-digit codes uniquely identify US states (first 2 digits) and counties (last 3 digits), such as 48201 for Harris County, TX. APNLookup automatically resolves the FIPS code for every standardized parcel.
9. What are the specifications of the Developer REST API?
The APNLookup API operates over HTTPS at https://apnlookup.org/api/v1/apn/standardize. It processes single and batch requests with <10ms average latency, returning structured JSON with canonical keys, county names, and direct GIS endpoints.
10. What are the rate limits for the Free vs Developer Pro ($29/mo) tiers?
• Free Web Usage: 100 requests per day via browser.
• Developer Pro ($29/mo): Unlimited programmatic REST API requests, 100 req/sec throughput, and bulk batch CSV processing.
11. How do direct county GIS web map links work?
For each matched county, APNLookup returns verified URLs to official county Esri ArcGIS parcel viewers, enabling proptech applications to deep-link directly into county parcel boundary polygons.
12. Can I clean and normalize a list of 10,000+ parcels via CSV?
Yes. Developer Pro subscribers can upload CSV spreadsheets of raw, messy parcel numbers and download a standardized file with verified canonical keys, county FIPS codes, and GIS URLs.
13. Which special characters are sanitized during normalization?
The engine automatically strips periods, colons, slashes, backslashes, tabs, and irregular whitespace, leaving only clean digits and inserting uniform canonical hyphens according to county rules.
14. What are the primary proptech use cases for APNLookup?
Title insurance title plants, automated valuation models (AVMs), property tax appeal consultants, surplus asset recovery locators, and mortgage loan origination platforms use APNLookup to eliminate database join errors.
15. How does Developer API key authentication work?
Keys use offline cryptographic HMAC SHA-256 signatures: apn_live_<HASH>. Authentication executes in sub-millisecond time on edge proxies with zero third-party latency.
16. How do I start integrating APNLookup into my application?
1. Test sample parcels in the APN Standardizer web tool.
2. Review the Developer API code examples in Python, JavaScript, and cURL.
3. Subscribe to Developer Pro ($29/mo) to receive your production API key.
4. Integrate the JSON endpoint into your data ingestion pipeline.