USPS® Address Verification | Free Tools and Best Options

USPS address verification webpage

USPS Address Verification is a process which ensures that a US mailing address is valid according to the USPS Coding Accuracy Support System (CASS) standards and that the address can receive mail. Address verification against the USPS database can reduce mailing cost, decrease lost or returned mail and speed up delivery.

The USPS is a good source for verifying addresses but the Postal Service also has several unique limits that may prevent them from being usable for you.

Do you want to know what these limits are and how they impact users? Great, we will cover limits with the USPS Terms of Service, address coverage, downtime, metadata, rate-limiting, and several other topics you should know about.

Here at Smarty, we offer blazing fast, USPS address verification tools with even broader application options than what the USPS delivers.

You can use them here:

USPS Address Verification Bulk USPS Address Validation USPS Address Verification API

In this article we’ll cover:

Why USPS Address Validation?

USPS Address Validation tells you that the US postal addresses you’re sending to are real and mailable. There are many factors that stand in the way of knowing if addresses will work for your purposes. ZIP Code changes, new construction, and annexation all play a role. Even human error when typing in addresses creates problems.

  • 10-20 new ZIP Codes are created each year and it can take up to 5 years for people to fully utilize a new ZIP Code.
  • An individual ZIP+4 Code may change up to once a month since it is tied to how many employees a post office has and who is working a particular route.
  • It’s estimated that between 4.7% and 8.4% of the time a customer fills out an online form or enters their information, they make a mistake. Depending on how large your database is, that could be a lot of incorrect addresses.

If you want mail to make it to the correct destination on the first try without losing packages or getting returned mail, address verification is an essential step.

The most obvious answer to this challenge is to use the USPS Address Verification web-tool to clean up your mailing address list. USPS address verification is free, but you might find there are other solutions that better fit your needs.

First, let’s talk about how to use the address verification tool from the USPS. We will also cover key pros and cons of the service. This article primarily covers the USPS Address Verification Web Tools, but we also cover the USPS Address Verification APIs in depth here.

How to Validate an Address with the USPS Address Lookup Tool

Even if you’re very confident in your mailing list quality, to qualify for presorted commercial mail rates, you must use an address checker to verify the 5-digit ZIP Code of all your US postal addresses within 12 months of mailing. We suggest checking addresses within a month before mailing since the USPS database publishes updates each month.

The USPS offers a free tool on their website to look up ZIP Codes by entering addresses one at a time. Here is how to validate an address with USPS and how to understand the results:

  1. Visit the USPS ZIP Code Lookup Page
  2. The minimum data the USPS Address Verification Tool permits is the street address, city, and state. If needed, the fields labeled for Apartment/Suite and ZIP Code can be left blank.
  3. If known, add the ZIP Code and the Apartment / Suite if applicable since it will improve the probability that the USPS address lookup tool will find the correct address.
  4. Click “Find”
  5. The tool will then run your address lookup against the USPS official address database to attempt to find a match.
  6. At this point, depending on what you entered, USPS will show you:
    1. a list of addresses if multiple valid matching addresses were found like this: USPS full verified address with a ZIP+4 appended.
    2. a single fully enumerated address including ZIP+4 Code if only one matching address was found. The address will also be listed in the official USPS standardized format like this: USPS full verified address with a ZIP+4 appended.
    3. an incomplete address missing the +4 Code. This means that only a partial match was found. E.g. USPS successfully found the city and state but failed to find the building or house number like this: Incomplete address missing ZIP+4 Code - Indicates partial match.
  7. You will also be able to click on the "⌄" icon for the listed address to expand the results. Possible Delivery Point Validation Indicator Options are:
    DPV Confirmation Indicator Mailable? Meaning
    Y Address is fully valid and shippable.
    D Primary number (building, house) confirmed but secondary number (suite, apartment, unit, etc.) missing from user entry.
    S Primary number (building, house) confirmed, secondary number (suite, apartment, unit, etc.) present but failed DPV Confirmation.
    N Primary number (building, house) and secondary number (suite, apartment, unit, etc.) failed DPV confirmation.
    - Address match for entered address was not found, so wasn’t submitted for DPV confirmation.

    The DPV Confirmation Indicator of “Y” is the response you most want, since it means it is the most precise address for a delivery location offered by USPS.

    A DPV Confirmation Indicator of “D” is almost as good since it indicates an address that is valid and shippable, but also indicates that there may be a valid secondary address number (suites, apartments, units, etc.) missing from your entry. This is useful since “D” acts as a flag that the address may require manual review to confirm the address doesn’t need an apartment, suite or unit number. The “D” indicator has prevented many lost packages.

    Mailing to an address with DPV Confirmation Indicator “D” typically means that your mail gets to the lobby of a building rather than a particular apartment or suite.

Note: The USPS address verification process does not confirm that a person or company works or lives at a specific address. Instead, the verification process confirms that an address exists and can receive mail.

As noted in step 7 above, if you click the "⌄" icon, you can expand the results and get up to 14 additional metadata points.

Looking at this output provided by the USPS Address Validation Tool, you might be wondering what things like "LAC", "eLot", and "DPV Confirmation Indicator" really are and how they can be used. While some of the metadata points aren’t relevant or important for most users, we’ll briefly explain a few useful ones.

Delivery Point Validation

Delivery Point Validation™ (DPV®) is a form of address validation designed by the USPS to ensure that an address can receive mail.

A delivery point can be a PO box, a box on an aircraft carrier, or a mailbox at the curb. It can also be a mail slot in the front door or a cluster mailbox in a subdivision—whatever the intended final destination is for a letter or package. Delivery points are not street addresses. A single street address may have multiple delivery points, such as individual units in apartment buildings or offices.

To identify delivery points individually, the USPS gives each one a unique 11-digit number, composed of the delivery point's nine-digit ZIP+4 Code plus an extra two digits that narrow the designation to the delivery point itself. This is the Delivery Point Code (DPC).

An address with a valid ZIP+4 Code but without a valid DPC may identify a building that is unused, a building that does not exist, or a vacant lot. Knowing how a valid delivery point differs from a valid address makes USPS output easier to understand.

LACS and LACSLink®

Another metadata point that shows up is LAC™.

Occasionally, addresses get renamed or renumbered. For example, there are many rural addresses that have been updated with more modern, easy-to-find city-street addresses in order to aid 911 emergency response teams. Or sometimes a city might rename a street to update an insensitive street name or honor influential local citizens. For example, In 2010, Minneapolis renamed a portion of 3rd Avenue North near Target Field to “Twins Way.”

To keep track of these changes, the USPS has a system called LACS.

LACS (Locatable Address Conversion System) is a secure dataset of rural-style addresses converted to city-style addresses that primarily arise from the implementation of the e911 system. It also contains existing city-style addresses that have been renamed or renumbered.

LACSLink® exists as the link between USPS address tools to check addresses against the LACS dataset.

Your metadata results will tell you if the address you entered has been checked against LACSLink®.

For example, try entering:


The USPS ZIP Code Lookup will return:

GREENBRIER TN 37073-5833

I know what you’re thinking. Either we put a typo in this article or the USPS is returning a totally different address from what you entered!

But when you expand your results you’ll see an "L" under the LAC. This means the address returned "5257 N" is the matching updated version of the address entered "2737 N" found in the LAC database and "5257 N" is the address that should be used.

Since these are primarily for rural addresses that were updated to match a more conventional city address format, you may not run across this type of address frequently if you’re only validating a handful of addresses.

If you’re cleansing several thousand addresses in your database or preparing a mass mailing, you’re bound to see it come up far more frequently.

Pros of Using the USPS Postal Address Verification Tool

If you only need to use an address checker to verify USPS addresses occasionally, the USPS Zip Code Lookup tool is a great way to validate US postal addresses one at a time. It’s easy to use, free, and requires no setup.

The tool also returns addresses in USPS standardized format. While this may look a bit different from what you originally entered, using the USPS standardized street address format ensures your mailpieces are processed smoothly with no delays.

With a little bit more work, developers can also integrate USPS Web Tools® APIs into a website or shipping application—also for free.

6 Cons of Using the USPS Postal Address Verification Tool

It’s pretty great that the USPS offers all these address validation options for free. But…you guessed it…there’s a catch. Actually there are 6.

  1. Slow User Experience

    If you want to grab an entire address, paste it into the USPS Address Verification Tool, hit enter, and see if your address is valid; you’re going to be disappointed.

    USPS requires that you enter each part of the address into a different field. After hitting the “Find” button, you go to a new page with the results and then click the "⌄" icon to see the full output. Then, you have to click another button if you need to make changes to the entered address or enter a new address.

    This isn’t so bad if you’re doing a few postal addresses, but it becomes painful around the 7th, and excruciating around the 14th.

    Smarty offers USPS address verification via single field entry. The response shows on the same page–which makes updating or entering the next address a breeze.

    Even if you use the USPS API for address verification, you’re still limited to no more than 5 addresses per second which is slow considering that other services can easily process 1000 times that amount in the same time.

  2. No Address Autocomplete

    Maintaining a clean address database starts at the beginning—when you first enter an address. Autocomplete prevents malformed data from making its way into your database by recommending only valid addresses while the user types.

    Unfortunately, the address verification tools offered by the USPS do not include an autocomplete feature which means:

    1. Address will take longer to enter
    2. Address are more likely to contain typos
    3. Address is more likely to be missing components
    4. An extra step will be required to confirm the address

    If you’re providing an online form for customers to enter address data, you definitely want to integrate Smarty's US Address Autocomplete into your forms to avoid user error when typing and also reduce friction for your customer.

    Learn more about what to look for in an address autocomplete service.

  3. Missing 15 Million+ US Addresses

    The United States Postal Service database contains 160 million mailing addresses in the United States.

    But did you know there are over 15 million NON-postal addresses out there? These are valid addresses that are serviced by private carriers like FedEx, UPS, and DHL. If you’re only going by the USPS database, you could be missing out on millions of valid customer addresses. To validate non-postal addresses, you’ll need to look beyond the APIs offered by the USPS.

  4. No International Data

    As the very name implies, the USPS is the United States Postal Service and while you can use the USPS to ship a package to an international location, the USPS does not offer any services to verify, validate, standardize or parse international addresses.

    If you need international address verification for any other country, you’re going to need to find another solution.

  5. Lacking Useful Metadata

    Remember when we talked about DPV, LACSLink, and the other metadata you can get from the USPS Address Validator?

    Not to be confused with the metaverse, metadata is data about data. It’s like the key to a map– explaining all the lines, dots, and other symbols. Metadata helps you sort and catalog information. The more metadata you have, the more you know about your original data or object, and the faster you can draw conclusions or analyze data.

    The USPS Web Tools can return the following data points:

    Firm name State Carrier route DPV footnotes
    Address1 5-digit ZIP Code Footnotes RDI
    Address2 ZIP+4 Code DPV match code Central delivery point
    City Delivery point CMRA Vacancy status

    Smarty US Address Verificationreturns all the USPS data points above plus the following:

    Defaut city name Building default indicator Daylight savings time flag SuiteLink
    ZIP-type Latitude and longitude No_stat flag
    EWS match Time Zone LACSLink code
    Congressional district Time zone offset LACSLink indicator

    With every validated address, Smarty can provide up to 45 points of metadata to enrich your data. That’s a lot more information you could be using to provide better, faster services.

  6. Strict Terms of Service (TOS)

    Yes, those things no one ever reads, but checks the box saying they’ve read them. In this case, any business that is planning to depend on USPS services should at least see this statement from the USPS web tools user guide:

    The Address Validation APIs can be used in conjunction with USPS SHIPPING OR MAILING SERVICES ONLY.

    The Address API must only be used on an individual transactional basis, i.e. not batch processing or cleansing of a database, but as a customer enters the information into a form on a website.

    Failure to comply with these terms and conditions can result in termination of USPS API access without prior notice.”

    Here are a few common use cases ruled out in the above USPS statement.

    • Want to clean your database of 1 billion, 1 million or 100 addresses with USPS? Sorry, USPS gives a resounding “No”.
    • Want to just run a quick batch of 20 addresses? Nope, that is also against the USPS TOS.
    • Want to make sure the address is valid before you ship a package with UPS since you recently found out that the UPS validator doesn’t verify building numbers or unit numbers? Unfortunately, the USPS TOS blocks you again.

    The TOS declare that USPS web services are to be used exclusively for USPS shipping or mailing services.

    The Terms also state that there is no Service Level Agreement (SLA). A service level agreement is a commitment between a service provider like USPS and a client that guarantees a minimum level of service.

    Without an SLA, USPS is quite literally offering no promises.

The USPS Address validation tools can also be accessed programmatically through a series of a suite of APIs. We discuss pros and cons of the USPS Address Verification APIs here.


USPS offers a good set of free-to-use tools and resources. Depending on your needs, address verification offered by USPS may be exactly what you need.

Here are all the abilities and limitations of USPS address verification that we discussed and how Smarty compares.

USPS Smarty
Verifies Full USPS Addresses
Standardizes Addresses
Parses Address
Single Field Address Entry
Address Autocomplete
15mm Non-Postal Addresses
Free to use? ✅*
Max Addresses Lookups Per Request 5
Lookups per second ~5 100,000+
Included output data
Supports International Addresses
Can be used for shipping UPS, FedEx, and other shippers
Database Cleansing Permitted
Bulk Address Verification Permitted
Guaranteed speed and reliability
Phone, email, and chat support
*30 day, 1,000 lookup trial. 250/mo free thereafter

Yes. The address verification tools offered by the USPS are free and simple to use—but come with limitations. Only you can determine if these limitations are deal-breakers.

If you’re looking for a long-term solution with the power and features you need to get the most out of your address data and help you maintain a clean database, Smarty US Address Verification might be what you need.

With US Address Verification by Smarty, you get the fastest and most accurate single address verification, bulk address validation, and address validation APIs on the planet. You’ll benefit from:

  • Enhanced address matching
  • All USPS database addresses
  • 15+ million non-postal addresses
  • Standardized address data
  • Additional metadata
  • Great documentation
  • Lightning-fast speeds
  • Legendary support

Check out the demo on our site or sign up for a 30-day free trial.

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