Smarty
Zipcodestack
PostalDataPI
Geoco.io
Melissa Data Quality
Loqate
usZIPCodes.org
REST API for US ZIP, ZIP+4, and Canadian postal codes. Single unified endpoint covers address validation and standardization, radius search (centroid haversine and true spatial polygon intersection), point-to-point distance, autocomplete/typeah

The modern platform for creating, sharing, and collaborating on AI prompts. Advanced version control and real-time testing.

Website, pricing, platforms and company facts side by side.
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ZIP Code API
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| Website | zip-codes.com | diffyn.com |
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| Company | Startup from the United States · 2026 | — |
| Listed in |
In their own words, as submitted to SaaSHub.

API for US ZIP, ZIP+4, and Canadian postal code data. One unified endpoint set covers North America — no separate APIs by country or data type. What it does Address validation and standardization — production-grade parser with ZIP+4 append, refreshed monthly Radius search — centroid haversine and...
No description of Diffyn yet.
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The Ultimate Prompt Tool for Creators – Visualize & Organize with Diffyn
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As answered by people managing ZIP Code API and Diffyn.
Diffyn's answer:
Addresses workflow and change management on LLM prompts, provide teams with traceability and visualization of tests across multiple models, provide deeper understading into efficiency of these prompts.
Diffyn's answer:
Diffyn is the platform that specializes on both change management and multi-model analysis.
Diffyn's answer:
React, Next.js, POSTGRESQL
Diffyn's answer:
Professionals incorporating LLMs or AI tools in their workflow and wants to keep track of changes and test their prompts.
Diffyn's answer:
I started working on Diffyn when I notice that prompting has become an essential part of work across many industries. While there are version control platofrms like github, they are not designed for just prompt management are can be overkill such applications, it is also not integrated natively with various LLMs and relevant tools for users to validate ideas and visualise results properly.
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When comparing ZIP Code API and Diffyn, you can also consider the following products.

Smarty provides address validation, autocomplete, geocoding and reverse geocoding services covering addresses in over 240+ countries.
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Free Zip Code API - Free Postal Code Validation | Zipcodestack
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The most affordable postal code API. 240+ countries, sub-5 ms responses. Simple, elegant, transparent.
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ridiculously cheap bulk geocoding turn US street addresses into map coordinates and map coordinates into street addresses using our straightforward REST API
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Melissa helps companies to harness Big Data, legacy data, and people data (names, addresses, phone numbers, and emails).
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