Microsoft-owned GitHub has blocked Spanish users from accessing an app designed to help Catalan independence protesters.
It follows a takedown request by the Spanish military police.
Authorities described the Tsunami Democràtic group, which is behind the app, as a "criminal organisation" which incites riots.
GitHub said it always complied with lawful requests.
A spokesman said: "Although we may not always agree with those laws, we may need to block content if we receive a valid request from a government official so that our users in that jurisdiction may continue to have access to GitHub to collaborate and build software."
GitHub has received takedown requests from China and Russia, related to different posts.
From hosting to protests
San Francisco-based GitHub provides hosting for software developers and allows coders to collaborate with each other.
It was bought by Microsoft in 2018 for $7.5bn (£5.8bn).
Tsunami Democràtic used GitHub to develop tools to co-ordinate protest action, including an encrypted communication app.
The group helped to organise pro-independence rallies at Barcelona airport, which saw dozens of flights cancelled.
Protestors demonstrating against the imprisonment of nine Catalan separatist leaders have copied tactics devised by demonstrators in Hong Kong, including blocking airports and using encrypted messaging.
This is not the first time a company has removed an app linked to protests.
Earlier this month, Apple removed an app which protesters in Hong Kong used to track police movements, claiming it violated the company's rules.
Tsunami Democràtic told TechCrunch that users of Apple's iPhone can't yet download the app because the "politics of the App Store is very restrictive".
The app is currently only available as a raw Android file, and users cannot download it via the Google Play store either.
The Spanish military police, or Guardia Civil, said protestors had engaged in "sabotage" of Spain's main infrastructure.
GitHub's website says it follows a four-step process each time it receives a takedown request.
This includes notifying affected users and giving them the chance to dispute any request.
It also says it tries to "limit the geographic scope of the takedown when possible".
Joe Brew, an independent data scientist, said the ban was likely to be ineffective.
"Trying to ban these types of things is like a game of cat-and-mouse. The moment you succeed with a ban in one place, it pops up in ten other places."