Elizabeth Parker
US address verification and deliverability for sthan.io
Elizabeth writes about what address verification does and how to judge it: what a verification answer contains, what the deliverability codes mean, how standardization differs from verification and cleansing, and how to test an API's accuracy yourself.
Her articles put live API responses next to the postal rules they come from, so you can see each change and the rule behind it.
- 5 articles
- 41 minutes of reading
- Live responses in every article
- Latest: Oct 7, 2026
What Elizabeth covers
- The basics Complete Guide to Address Verification APIs in 2026what verification is, how to choose an API, and common pitfalls
- Reading a verification answer What an Address Verification API Returns, Field by Fieldevery field of one real response, and the DPV codes Y, D, S and N
- The vocabulary Address Cleansing vs Verification vs Standardizationfour terms vendors use loosely, plus a 10,000-row cleansing run
- Postal formatting Address Standardization API: What Changes, With Examplesthe Publication 28 rules, with three before-and-after responses
- Judging a vendor How to Test an Address API's Accuracybuild a truth set, damage it, and score five numbers
Where to start
A reading order for someone choosing or checking an address verification API.
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Start here: what verification is, why it matters, and what to look for in an API.
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Learn to read the answer: deliverability status, DPV codes, and what a confirmed address does and does not tell you.
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Work out which step your data needs, with the results of cleansing a 10,000-row file.
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See exactly what standardization changes, rule by rule.
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Before you commit to a vendor, test it on your own addresses with five numbers.
Questions these articles answer
Each question links to the answer inside the article.
The basics
- What is an address verification API? Complete guide
- What's the difference between address validation and address verification? Complete guide
- Is address standardization the same as verification? Standardization API
- What is address cleansing? Cleansing vs verification
- Which step do I need? Cleansing vs verification
Reading the answer
- What do DPV codes Y, D, S and N mean? What a verification API returns
- Does a confirmed address mean someone lives there? What a verification API returns
- What does ConfirmedPrimaryOnly mean in a sthan.io response? What a verification API returns
- Should standardized addresses be in uppercase? Standardization API
- Should I write # or APT for an apartment? Standardization API
Testing and data quality
- How many addresses do I need to test an address API? Testing accuracy
- What is a silent substitution? Testing accuracy
- Should an address API ever return nothing? Testing accuracy
- How much of an address list needs fixing? Cleansing vs verification
- How accurate are address verification APIs? Complete guide
Building and cost
- Should I verify addresses on the client-side or server-side? Complete guide
- How much does address verification cost? Complete guide
- How does address verification reduce shipping costs? Complete guide
What these articles rely on
- Postal rules
- USPS Publication 28, cited by section
- Live calls
- sthan.io verification and parser responses, each dated in the article
- Other vendors
- Documentation and glossaries from Google, Smarty, Lob, EasyPost and Loqate
- Real data
- A 10,000-row Address Cleaner run (Oct 12 to 13, 2026) checked row by row, and the parser benchmark of 26,943 damaged addresses
- Read dates
- Oct 3 to 7, 2026, listed at the end of each of the four 2026 articles
Related on sthan.io
Terms explained
All articles by Elizabeth
Address Standardization API: What Changes, With Examples
What an address standardization API changes, rule by rule from Publication 28, with three live before-and-after examples and four APIs compared.
Address Cleansing vs Verification vs Standardization
Four terms vendors use loosely, defined from Smarty, Loqate and Publication 28, with one address run live through a parser and a verification call.
What an Address Verification API Returns, Field by Field
One real response with every field explained, what the DPV codes Y, D, S and N mean, and the same answers under five vendors' field names.
How to Test an Address API's Accuracy
Build a truth set, damage it in controlled ways, and score five numbers: recovery, silent errors, flagged errors, empty results and refusal of fake addresses.
Complete Guide to Address Verification APIs in 2026
Master address verification with our comprehensive guide covering API selection, implementation, and best practices.