Blog
Migration guides, pricing teardowns, customs and address-data explainers, and the engineering behind the API.
45 posts
Topics: Pricing (16), USPS v3 (16), Address validation (15), Vendor comparison (13), Web Tools migration (7), Districts (5), Redistricting (5), Troubleshooting (4), USPS license (4), OAuth (3), Quickstart (3), Rate limits (3), API governance (2), Customs (2), EasyPost (2), Ecommerce platforms (2), International shipping (2), Migration (2), USPS enrollment (2), Architecture (1), BYOK (1), Checkout (1), Data quality (1), PHP (1), Political mail (1), Reference (1), SDK (1), SDKs (1), Tracking (1)
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8 min read Comparison
Radar vs RevAddress: Address Validation and USPS Deliverability Compared (2026)
Radar sells US address validation on annual enterprise plans from $2.00 per 1,000 calls. RevAddress returns the USPS DPV code and flags on a self-serve key.
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10 min read Comparison
Service Objects vs RevAddress: What Quote-Only Address Validation Pricing Costs in 2026
Service Objects DOTS Address Validation is quote-only and CASS-certified. What its free trial is, what a quote must pin down, and what flat pricing buys.
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7 min read Customs
CN22 vs CP72: Why USPS Chooses the Customs Form
USPS selects the customs form from content type and weight. Learn what the label request actually controls, what prints, and which descriptions fail.
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8 min read Field guide
What an Address File Audit Finds Before the Next Mailing
See the eight questions an address file audit should answer: match quality, ZIP damage, duplicates, geography, vacancy, list decay, repairs, and waste.
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9 min read News
Ten States Redrew Their Congressional Maps. The Address Data Hasn't Caught Up.
The Census Bureau's official district files arrive in September, weeks before the year's heaviest political mail. What that means if you mail by district.
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7 min read Guide
Which States Have New Congressional Maps for 2026? The Full List, With Dates
Every state with a new U.S. House map for 2026: how each was adopted, when it was enacted, and where the litigation stands, with official sources.
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5 min read News
North Carolina's New Congressional Map: What Moved for 2026
SL 2025-95 redrew North Carolina's U.S. House map for 2026. What moved in the First and Third Districts, the litigation, and the voting calendar.
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6 min read Guide
What Congressional District Am I In? In Ten States, There Are Two Answers
How to look up your congressional district, and why in the states that redrew for 2026 the district you are in and the district you vote in differ.
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6 min read Guide
Where Do I Vote in Texas? What the New Map Changes — and What It Doesn't
Your Texas polling place is set by your county, not the congressional map. What PLANC2333 changes on your November ballot, and how to check it.
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9 min read Guide
How to Find the HS Code for Anything You Ship (2026)
A three-minute method for finding the right HS, HTS, or Schedule B code: worked examples from the live US tariff schedule and the fields USPS validates.
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8 min read Comparison
Geocodio vs RevAddress — The 2026 Price Increase and the CASS Gap
Geocodio doubled pay-as-you-go pricing in February 2026 and still isn't CASS/DPV certified. Where it wins, where it falls short, and a USPS-native option.
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9 min read Comparison
Experian Address Validation (QAS) vs RevAddress: What Quote-Only Pricing Actually Costs You in 2026
Experian's Address Validate API is quote-only: 1 credit per successful lookup, price on request. What to ask for, and what published flat pricing buys.
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9 min read Comparison
PostGrid vs RevAddress: Address Validation Compared (2026)
PostGrid bills US address verification from $18 a month with a per-lookup geocoding surcharge. What it includes, what it does not, and where each one fits.
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9 min read Comparison
Loqate vs RevAddress: What Address Verification Costs in 2026
Loqate publishes 4.1 to 4.7 cents a lookup for US address capture and quotes verification on request. What that costs at volume, against a flat plan.
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10 min read Comparison
Melissa Address Verification Pricing in 2026: What Three Credits Per US Address Actually Costs
Melissa bills US address verification in credits: 3 per address, so a $40 pack of 10,000 credits is about 3,300 lookups. The real per-lookup math for 2026.
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9 min read Comparison
Lob vs RevAddress: Address Verification Pricing and the Plan Underneath It
Lob's cheap verification bundles ride direct-mail plans that start at $260/mo. The published August 2026 rates, DPV depth, and when each is right.
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10 min read Comparison
Google Address Validation API Pricing in 2026: The Per-Request Curve, the CASS Option, and the 30-Day Caching Rule
Google's Address Validation API costs $17 per 1,000 calls after 5,000 free, and its terms cap caching at 30 days. The real curve, and when flat pricing wins.
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6 min read SDK
RevAddress Checkout Guard: Drop-In Address Risk Widget
One script tag adds inline address checking to any address form you control. The real contract: attributes, badge states, sandbox keys, and how it fails.
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9 min read Comparison
Smarty vs RevAddress: Address Validation API Compared (2026)
Smarty's US Address Verification runs $17 to $485 a month by volume, checked August 2026. What that buys, and what a flat USPS-native plan costs instead.
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9 min read Migration guide
EasyPost March 17 Deadline: What Auto-Enrollment Cost, and Your Options Now
EasyPost auto-enrolled accounts on March 17, 2026. What Free Access and BYOCA actually cost at volume, and how to decide which one you should be on.
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13 min read Migration guide
EasyPost to USPS API Migration: Every Call, Mapped
Map every EasyPost call to a USPS v3 endpoint: validation, rates, tracking, labels. Working code in three languages, and the license step that gates labels.
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9 min read Comparison
EasyPost vs RevAddress: USPS Shipping API Pricing Compared
EasyPost gives you 3,000 free labels and 100+ carriers. RevAddress is flat-rate and USPS-only. Where the crossover sits, and what each bill actually covers.
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9 min read Migration guide
Magento USPS AC-15210: Apply the Patch, Then Fix the Three Things It Leaves Broken
AC-15210 is Adobe's official USPS REST patch, not an unfixed bug. How to apply it, the config.xml error it ships with, and the gaps it leaves behind.
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9 min read Comparison
ShipEngine vs RevAddress: What the ShipStation API Rename Changes for USPS Teams
ShipEngine is becoming ShipStation API. The published August 2026 plans, the per-endpoint quota most comparisons miss, and when each is right.
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11 min read Comparison
Shipping API Comparison 2026: EasyPost, Shippo, ShipEngine, RevAddress
EasyPost, Shippo, ShipEngine and RevAddress compared on published rates: labels, tracking, address lookups, USPS fees, and the fitting volume for each.
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9 min read Comparison
Shippo vs RevAddress: Per-Label Fees, Per-Validation Fees, and Flat Plans
Shippo bills $0.07 a label and $0.02 an address validation as of August 2026. What that costs at volume against a flat plan, and when Shippo wins.
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9 min read Technical analysis
USPS API Access Control: What April 1, 2026 Actually Changed
USPS switched tracking from possession-based to identity-based access on April 1, 2026. What landed, who it hit, and how it led to the August license.
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9 min read Replacement guide
usps-api and usps-webtools Are Dead: the 2026 Replacement
The usps-api, usps-webtools, and usps-webtools-promise packages target an API that no longer exists. The errors you are seeing, and the one-command swap.
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8 min read Guide
USPS API Pricing 2026 — What It Actually Costs
USPS address validation stopped being free on August 1, 2026. The published fee curve, the license that gates it, and what direct vs third-party costs.
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12 min read Breaking change
USPS API Rate Limits in 2026: From 6,000/min to 60/hour
USPS v3 throughput fell from roughly 6,000 requests a minute on Web Tools to 60 per hour. What that does to checkout at peak, and five architecture patterns.
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8 min read Architecture
USPS April 2026 Access Control: The Architecture That Survived It
Access Control landed April 1 and the license regime followed on August 1. The integration shape that absorbed both, and the checks to run now.
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10 min read Tutorial
USPS Batch Address Validation: 50 Addresses per Call
Validate 50 US addresses in one request. The exact payloads, per-address failure handling, rate-limit backoff, and how to run a 10,000-row list through it.
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16 min read Onboarding
How to Get a USPS CRID and MID, and Link Them to the v3 API (2026)
A USPS CRID identifies the business; a MID identifies the mailer. Here is where to find them, connect the EPA, link COP claims, and activate v3 APIs.
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9 min read Troubleshooting
USPS v3 OAuth Troubleshooting: Every Error and How to Fix It
401, 403, and 429 from USPS v3, with the exact fix for each, including the Addresses API license that has gated address calls since August 1, 2026.
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9 min read Quickstart
USPS v3 Address Validation: One Request, Start to Finish
The USPS v3 address call in curl, Python and Node: OAuth, the required parameters, every DPV code, and the license USPS has required since August 1, 2026.
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15 min read Migration guide
USPS v3 Migration Guide: Node.js and Python, XML to REST
Every Web Tools operation rewritten in the usps-v3 Python and Node SDKs, with the exact method names, the field that silently fails, and a cutover playbook.
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12 min read Tutorial
USPS Node.js SDK Quickstart: TypeScript Client for the v3 API
Install usps-v3, authenticate once, and call address validation, tracking, rates, and labels from Node. Zero dependencies, typed errors, Express route.
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12 min read Tutorial
USPS v3 API with PHP: Complete Quickstart Guide
Install revaddress/usps-v3-php and call the USPS v3 REST API from PHP: validation, tracking, rates, labels, plus Magento, WooCommerce and Laravel wiring.
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11 min read Tutorial
USPS Python SDK Quickstart: Validate, Track, and Rate with usps-v3
Install usps-v3, authenticate once, and call address validation, tracking, and rates from Python. Working code, real return shapes, typed errors.
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9 min read SDK reference
USPS v3 SDK for Python and Node.js: Endpoints, Credentials, and the OAuth You Do Not Have to Write
The usps-v3 SDKs for Python and Node.js at v1.0.4. Real method signatures, which calls need Payment Authorization, error classes, and token handling.
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12 min read Reference
USPS Web Tools to v3 REST API: Complete Endpoint Mapping
Every Web Tools XML API mapped to its v3 REST route, with the auth change, the reversed address fields, and the gotchas that break production migrations.
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14 min read Migration
USPS Web Tools Migration Checklist (2026)
A numbered checklist for moving off USPS Web Tools XML: endpoint map, the license now required, OAuth, field mapping, error mapping, and the cutover.
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10 min read News
USPS Web Tools Shut Down on January 25, 2026: What Broke and the Fastest Way to the v3 API
USPS retired Web Tools on January 25, 2026. If ShippingAPI.dll, USERID, or secure.shippingapis.com is failing, map the XML route to v3 REST here.
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11 min read Migration guide
WooCommerce USPS Rates Not Showing: The 2026 Fix
USPS rates vanished from WooCommerce checkout when Web Tools retired. Update to 5.2.5, enter REST credentials, and cache against the 60-per-hour cap.
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12 min read Migration guide
USPS Web Tools Migration: XML to v3 REST, End to End
Every Web Tools endpoint mapped to its v3 REST equivalent, the OAuth flow in three languages, the field swap that corrupts addresses, and the 60/hr wall.