What is an Unofficial API?
An Unofficial API is an interface that enables programmatic access to data or functionality that providers don’t officially support.
When people hear this definition, they usually think of web scrapers, which are notoriously unreliable and obnoxious to maintain.
Unlike a web scraper, an Unofficial API is an interface built for continuous, bidirectional interaction. This has two important implications:
Unofficial APIs are optimized for executing atomic events, such as updating information about a single customer or fetching structured data from a new business found in a registrar.
Unofficial APIs require a ‘contract’ to be considered usable. There must be a clear maintainer and documented expectations for performance & change management. In other words, people must be able to trust that they can integrate the API into a workflow and use it reliably.
This can seem like a high bar, but it’s necessary to give Unofficial APIs credibility.
Infrastructure is never ready for major changes
Plaid started in 2013, when digital banking was becoming mainstream. Consumers wanted to manage their money online, but banking infrastructure was stuck in the 80s.
If Plaid waited for banks to catch up, they would’ve run out of cash. Instead, they built the infrastructure themselves to integrate with financial institutions, and proved to the industry that it needed better integrations.
It’s a tale as old as time — innovations drive the need for new infrastructure. The AI revolution is no different. Agents are really good at analyzing unstructured information and orchestrating a set of tasks. They perform best when they have a well-defined set of tools or functions that they can use.
The problem is that the number of use cases for agents is infinite, but APIs are not. This gap is widening as industries running on specialized vertical software demand AI-powered efficiency gains, but these core systems lack any APIs.
Once again, it’s impractical to wait for the infrastructure to catch up. Developers need to be able to integrate with any arbitrary website or app in a consistent, reliable way.
The time has come for Unofficial APIs to be mainstream
The key blocker to large scale adoption of Unofficial APIs has always been maintenance. Each integration has been bespoke code that only the original developer understands. When new features are added to an app or page layout changes, it can break the integration without warning and wake up the only developer who understands the code and the underlying system.
The game-changer? LLMs can solve the maintenance problem. They can quickly process unstructured documentation, make small tweaks to code and can identify root causes when paired with instrumentation. Best of all, when trained on tons of integration examples, work well at adapting to interface changes.
Browser automation tools try to solve the problem by creating an entirely new type of interface. They make for a slick demo and give the impression of being able to automate anything, but suffer from reliability and performance issues that make them impossible to use right now for any large scale application.
Why add an entirely new type of unpredictable interface to your stack, when developers actually want deterministic and reliable APIs?
Deliver what engineers need - consistent interfaces that work at scale, not flashy demos that will inevitably break in production.
Unofficial APIs in action in PropTech
Tons of PropTech companies rely on Zillow in some way to run their business. The problem? The most commonly used products, such as rental and listing management, sits behind a login with no API. This makes it complicated & expensive to integrate Zillow into an automated process.
The good news is that most PropTech companies have well-defined manual processes built around Zillow. This is where Unofficial APIs shine. Instead of brittle scraping or clunky browser automation, an Unofficial API provides:
A clean, RESTful interface to Zillow's data that feels just like an official API
Secure credential management handling both login and MFA
Predictable response formats that normalize Zillow's complex UI into structured data
Resilience against Zillow's frequent UI changes
For developers, the integration becomes a simple set of API calls that fit their existing workflow, not a complex automation system requiring constant babysitting. They can fetch property data on demand, run analytics, and report back to their customers without worrying about the underlying connection to Zillow breaking.
We’re seeing this same pattern play out in other industries like LegalTech, GovTech, InsureTech and Healthcare, where a lack of APIs are holding them back from innovating at pace.
The future of integrations is unofficial (but managed) APIs
Integrating with applications that already have clean, official APIs is easy. The real competitive advantage and value will come from augmenting those integrations with the long tail of systems that don't have great APIs—or any APIs at all.
But to be successful, these Unofficial APIs must be:
Managed with rigorous monitoring, testing, and maintenance protocols
Purpose-built to provide the exact functionality required by developers and reduce the need to manage complex schema mapping logic.
Reliable with SLAs that match or exceed those of official APIs
Developers that augment their existing API stack with unofficial ones will see the most benefits from AI and advanced automation. They'll integrate with systems previously considered impossible or too flaky to depend on programmatically.
Instead of waiting for infrastructure to catch up to AI, these developers will show the industry what’s possible.