This glossary defines the technical terms Fake Addresses uses across its guides, API docs, and locality pages — ZCTA, USPS Publication 28, non-deliverable, geographic coherence, and similar postal, geographic, and software-testing terms — each defined in plain language the first time a guide or reference page uses it.
This glossary collects every technical term Fake Addresses uses that a QA engineer, developer, or designer might not already know. That set spans postal terms borrowed from USPS Publication 28, geographic terms borrowed from the the national statistical agency, and product-specific terms like geographic coherence and postal-format-valid that describe exactly what Fake Addresses guarantees about its own output.
Each entry defines its term on first use, independent of any other page: a definition here should make sense read entirely on its own, without needing the guide or locality page that linked to it for context. That is deliberate — a search engine or an AI assistant answering a question about one of these terms may show this definition with nothing else around it.
Terms are listed alphabetically. Where a term has an official primary source — USPS Publication 28 for postal terms, the the national statistical agency for geographic terms, the Universal Postal Union for international terms — that source is linked directly from the definition, rather than paraphrased without attribution.
A term used inside a guide or a locality page's FAQ links back to its entry here the first time it appears on that page. That keeps a reader unfamiliar with a term like ZCTA or rate center from ever being left to guess.
ADDRFEAT is a the national statistical agency the street and boundary reference data data layer that records the address-number ranges assigned to each side of a real street segment. Fake Addresses checks every candidate street number against ADDRFEAT specifically to confirm the number falls outside any range already assigned there, which is one of the two checks, alongside other open address data, behind the non-deliverable guarantee.
An Address Verification System, or AVS, is a check retailers and payment processors run to compare the billing address entered on an order against the address a card issuer has on file for that card, used mainly to catch mismatched or fraudulent transactions. AVS checks a billing address against a financial record, not against USPS delivery data, so it is a different check from Delivery Point Validation.
CASS Certification (Coding Accuracy Support System) is a USPS program that certifies software correctly standardizes and validates US addresses against USPS data. Fake Addresses is not CASS-certified software, and does not attempt to be, because its purpose is the opposite of CASS's: generating addresses that are structurally correct but not deliverable, rather than validating and correcting real ones.
free to use is a Creative Commons legal tool that waives all copyright and related rights to the fullest extent possible, so a work can be used, copied, and modified without asking permission or providing attribution. Fake Addresses licenses all generated output under free to use, unlike some competing generators, which require attribution in their terms of service.
A dataset version is the specific build of Fake Addresses' underlying data — streets, ZCTAs, city tables, area codes — that a given record was generated against, stamped in the form YYYY.MM on every API response and export. A ?seed= value pinned to a specific dataset version returns the exact same record indefinitely, even after a newer dataset version ships.
Delivery Point Validation, or DPV, is a USPS check that confirms whether a specific street number on a specific street is an assigned, deliverable point on an actual mail route — a stricter check than basic format validation, which only confirms an address is structured correctly. Fake Addresses output deliberately fails Delivery Point Validation by design, while still passing format validation.
A FIPS code is a Federal Information Processing Standards identifier the U.S. government uses to uniquely label a state or county, independent of that place's name, which can change or be spelled inconsistently across data sources. Fake Addresses records a generated point's county FIPS code as one of the eight data attributes required for a locality to get its own page.
Geographic coherence is Fake Addresses' term for a record whose street, city, county, state, ZIP code, and area code are all derived from a single generated point, rather than assembled independently from separate lists that might not actually agree. It is the property that keeps a generated address from describing a city and ZIP code that do not correspond to each other.
The last-line city is the city name the Postal Service actually prints on the final line of a standardized address for a given ZIP code, which frequently differs from the U.S. the national statistical agency's official place name for the same area — common in unincorporated communities. Fake Addresses uses the USPS last-line city specifically, not the official place boundary name, for every generated record's city field.
Non-deliverable describes a Fake Addresses record whose street number falls outside every range the Postal Service has assigned to a delivery point on that street, confirmed by a nightly sample checked against live USPS Delivery Point Validation. It is a measured property, re-checked continuously, not an assumption made once and never verified again.
NPA, or Numbering Plan Area, is the formal term for what is commonly called an area code — the three-digit prefix assigned by the North American Numbering Plan to a specific geographic region. Fake Addresses assigns each generated US phone number an NPA that actually serves the record's county, then uses the 555-0100–555-0199 line range reserved for fiction.
Postal-format-valid describes a record that is structured and abbreviated correctly according to USPS Publication 28 for US addresses, or UPU S42 internationally — every field present, in the right order, with the right abbreviations — regardless of whether the address is actually deliverable. A record can be postal-format-valid and non-deliverable at the same time, which is exactly what Fake Addresses is built to produce.
A rate center is a geographic unit telecommunications carriers use to assign area codes and phone-number blocks, and it does not always align neatly with county or city boundaries. Fake Addresses maps a generated record's area code from the rate centers serving its county, which is why a single county can sometimes carry more than one valid area code.
Seed determinism is the guarantee that a specific seed value, combined with a specific dataset version, returns byte-identical output every time it is requested, indefinitely. Fake Addresses is the only generator in this category that publishes this guarantee, which is what makes its output usable as a stable, reproducible fixture in a CI pipeline.
the street and boundary reference data is the U.S. the national statistical agency's public-domain database of street geometry, boundaries, and geographic features, used to build the the national statistical agency's own maps and made freely available for anyone else to build on. Fake Addresses draws every real street name in its US output from the street and boundary reference data data, which is also the source for the ZCTA and county boundaries every generated point is checked against.
UPU S42 is the Universal Postal Union's international addressing-standard template, used to format a mailing address correctly for a specific country's postal conventions when the address is not a US address. Fake Addresses applies a UPU S42 template for any country where one is published, and labels a country's coherence level explicitly where no such template exists yet.
Source: Universal Postal Union
USPS Publication 28, Postal Addressing Standards, is the United States Postal Service's official reference for how a US mailing address should be formatted: line order, official street-suffix and directional abbreviations, unit designators, and rules for rural routes, PO boxes, and military addresses. Fake Addresses formats every US record against this same standard, which is what makes the output postal-format-valid.
A ZCTA, or ZIP Code Tabulation Area, is a the national statistical agency geographic area that approximates a USPS ZIP code for mapping and statistical analysis. The the national statistical agency builds ZCTAs from Census tabulation blocks rather than from the Postal Service's own point-based delivery data, so not every valid ZIP code has a matching 2020 ZCTA. Fake Addresses uses ZCTA boundaries as the geographic unit every generated US record is built inside.
ZIP+4 is a nine-digit extension of the standard five-digit ZIP code, adding four digits that narrow a delivery area down to a specific block, building, or group of mailboxes. USPS Publication 28 treats a ZIP+4 code as part of what makes an address "complete" for automated sorting purposes.
No. This glossary defines the vocabulary Fake Addresses uses across its guides and locality pages — terms like ZCTA and geographic coherence — in plain language. The data sources page instead lists which organizations that data actually comes from and under what license.
Yes. Every term on this page has its own anchor, so a link to a specific definition — for example this page's own URL followed by #zcta — points straight at that entry rather than the top of the glossary.