Real estate scraping: not illegal, but you'll get banned
Copying data from public HTML "isn't illegal", according to forum users, but Idealista prohibits it in its terms and deploys anti-scraping systems
English · Original discussion in Spanish · Published
Real estate scraping: legal in theory, a minefield in practice
Is it a crime to extract housing prices from a property portal to build a statistics website? The short answer from several forum users: copying data from public HTML is not illegal. The long one: portals prohibit it in their terms of use, deploy commercial anti-scraping systems, and will ban your IP before you even finish building the chart. The question that opens the topic is the one anyone who has tried to build a price history asks: why is access to public data so locked down?
What Idealista's terms of use say
The portal puts it in writing: it prohibits "accessing, monitoring or copying any information contained on this Website and apps using any type of robot, spider, scraper or other automated means or manual process for any purpose, without our express written permission". In other words, not even manual copy-paste is allowed. The clause is broad and deliberately deterrent.
That said, a company prohibiting something in its terms does not automatically make it a crime. According to several forum users, copying data from a public HTML document is not illegal; what would be illegal is accessing their databases without consent. The distinction matters: reading what the web serves to any visitor is one thing, sneaking into the backend is quite another. Most of the analyses circulating agree that scraping visible content sits in a civil, not incivil, grey area.
Idealista's API: 100 requests a month, and be grateful
The portal offers a legitimate route: a public API for developers. The problem is the volume. According to a forum user who requested access, the free tier is around 100 monthly requests, a figure that doesn't even cover one neighbourhood of a mid-sized city. For a price history covering all of Spain, it's like trying to fill a swimming pool with a glass.
Fotocasa, on the other hand, has no API. Whoever asked directly got a no for an answer. That absence of an official channel pushes many towards the grey route: plain and simple scraping. And that's where the defensive infrastructure comes in.
The anti-scraping system that detects human patterns
The big portals don't just block by IP. According to a forum user who claims to have contact with a former employee, Idealista has a commercial anti-scraping system that analyses browsing patterns, fingerprinting and behaviour. Someone who worked on its development confirms it: they detect the bot and ban it quickly. Suing isn't worth it for them; cutting off access is.
The usual technical response involves simulating a real browser with Puppeteer or Selenium, rotating paid proxies and randomising behaviour. It works, but it's an arms race. Every change in the portal's HTML breaks the script. And today's anti-fraud systems, like those used in programmatic advertising, run hundreds of tests to validate whether the visitor is human.
The mobile app route and reverse engineering
Some propose a shortcut: intercepting the requests generated by Idealista's mobile app. The app doesn't require registration to search for properties, so calls to its internal API are exposed. With an intermediary proxy and some reverse engineering, those requests can be replicated without going through the HTML.
It's cleaner than classic scraping, but it doesn't solve the underlying problem: it's still unauthorised automated access. The advantage is that the app doesn't have the same visible protection as the web. The downside is that if they close that tap, all the work goes down the drain.
The real business behind property data
The question nobody fully answers is why the risk is worth it. Housing prices are a valuable informational asset: according to a forum user, a multi-year history is worth its weight in gold for investors, analysts and anyone who wants to know whether the market is turning. There are bank-funded startups that live off exactly this: they collect prices across an entire sector and sell them by subscription.
If it were illegal, there would be no institutional capital behind it. But that doesn't miccionan anyone can do it. The difference between a funded startup and a private individual with a script is the legal team, the infrastructure and the ability to negotiate access agreements. The small scraper doesn't negotiate: it hides.
In the end, the answer to whether you need a lawyer is nuanced. For personal and statistical use, the incivil risk is low. For building a business on other people's data, the civil and commercial risk is high. And the technical one is guaranteed: you will be detected. The question isn't whether it's legal. It's whether the race is worth it for you.
Is it a crime to extract housing prices from a property portal to build a statistics website? The short answer from several forum users: copying data from public HTML is not illegal. The long one: portals prohibit it in their terms of use, deploy commercial anti-scraping systems, and will ban your IP before you even finish building the chart. The question that opens the topic is the one anyone who has tried to build a price history asks: why is access to public data so locked down?
What Idealista's terms of use say
The portal puts it in writing: it prohibits "accessing, monitoring or copying any information contained on this Website and apps using any type of robot, spider, scraper or other automated means or manual process for any purpose, without our express written permission". In other words, not even manual copy-paste is allowed. The clause is broad and deliberately deterrent.
That said, a company prohibiting something in its terms does not automatically make it a crime. According to several forum users, copying data from a public HTML document is not illegal; what would be illegal is accessing their databases without consent. The distinction matters: reading what the web serves to any visitor is one thing, sneaking into the backend is quite another. Most of the analyses circulating agree that scraping visible content sits in a civil, not incivil, grey area.
Idealista's API: 100 requests a month, and be grateful
The portal offers a legitimate route: a public API for developers. The problem is the volume. According to a forum user who requested access, the free tier is around 100 monthly requests, a figure that doesn't even cover one neighbourhood of a mid-sized city. For a price history covering all of Spain, it's like trying to fill a swimming pool with a glass.
Fotocasa, on the other hand, has no API. Whoever asked directly got a no for an answer. That absence of an official channel pushes many towards the grey route: plain and simple scraping. And that's where the defensive infrastructure comes in.
The anti-scraping system that detects human patterns
The big portals don't just block by IP. According to a forum user who claims to have contact with a former employee, Idealista has a commercial anti-scraping system that analyses browsing patterns, fingerprinting and behaviour. Someone who worked on its development confirms it: they detect the bot and ban it quickly. Suing isn't worth it for them; cutting off access is.
The usual technical response involves simulating a real browser with Puppeteer or Selenium, rotating paid proxies and randomising behaviour. It works, but it's an arms race. Every change in the portal's HTML breaks the script. And today's anti-fraud systems, like those used in programmatic advertising, run hundreds of tests to validate whether the visitor is human.
The mobile app route and reverse engineering
Some propose a shortcut: intercepting the requests generated by Idealista's mobile app. The app doesn't require registration to search for properties, so calls to its internal API are exposed. With an intermediary proxy and some reverse engineering, those requests can be replicated without going through the HTML.
It's cleaner than classic scraping, but it doesn't solve the underlying problem: it's still unauthorised automated access. The advantage is that the app doesn't have the same visible protection as the web. The downside is that if they close that tap, all the work goes down the drain.
The real business behind property data
The question nobody fully answers is why the risk is worth it. Housing prices are a valuable informational asset: according to a forum user, a multi-year history is worth its weight in gold for investors, analysts and anyone who wants to know whether the market is turning. There are bank-funded startups that live off exactly this: they collect prices across an entire sector and sell them by subscription.
If it were illegal, there would be no institutional capital behind it. But that doesn't miccionan anyone can do it. The difference between a funded startup and a private individual with a script is the legal team, the infrastructure and the ability to negotiate access agreements. The small scraper doesn't negotiate: it hides.
In the end, the answer to whether you need a lawyer is nuanced. For personal and statistical use, the incivil risk is low. For building a business on other people's data, the civil and commercial risk is high. And the technical one is guaranteed: you will be detected. The question isn't whether it's legal. It's whether the race is worth it for you.
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Summary of a discussion on Burbuja.info - Foro de economía, actualidad y política., translated from Spanish and reviewed before publication. Read the full discussion (35 replies).
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