Postio.co.uk VS Diffyn

Postio.co.uk's answer

Postio charges only when a lookup returns a result — searching is free. Address, email and phone validation sit behind one API with a single JSON response envelope, so you integrate once rather than stitching three vendors together. Address data comes from Royal Mail's Postcode Address File under a direct licence, not scraped or resold sources. There are no tiers, contracts or minimum spend, and the first 100 lookups need no card.

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.

Postio.co.uk's answer

Pricing is published and pay-as-you-go: 2.2p per address, 1p per email, 1p per phone, billed only on a result. No sales call, no annual contract, no minimum commitment. You can be live in a few minutes with 100 free lookups and no card, and the same API covers all three validation types. For UK addresses specifically, the data is licensed directly from Royal Mail rather than obtained second-hand — which matters after the 2025 High Court ruling on database rights in this market.

Diffyn's answer:

Diffyn is the platform that specializes on both change management and multi-model analysis.

Postio.co.uk's answer

A REST API served from edge locations, with official SDKs for JavaScript/Node, Python, Go, PHP, Ruby and .NET, all open source on GitHub. The API is documented by a public OpenAPI specification.

Diffyn's answer:

React, Next.js, POSTGRESQL

Postio.co.uk's answer

Developers and technical teams building UK-facing forms — ecommerce checkouts, signup flows, CRM and logistics systems. Typically small to mid-sized product teams, agencies building for UK clients, and software vendors embedding address lookup in their own product. It suits anyone who wants a UK-accurate API without an enterprise procurement process.

Diffyn's answer:

Professionals incorporating LLMs or AI tools in their workflow and wants to keep track of changes and test their prompts.

Postio.co.uk's answer

Postio is a trading name of Onno Group Limited, registered in England & Wales (company no. 08622799). It was built to make Royal Mail PAF-accurate UK validation available on straightforward pay-as-you-go pricing, rather than the contracts and minimum commitments that have been standard in this market. Address, email and phone validation were brought together behind one consistent API so a team can solve all three at once.

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.

Postio.co.uk's answer

Serving a huge range of customers across the world looking for a blazing fast UK Address AIP product. From bootsrapped entrepreuners to FTSE 250 companies. We serve them all.