If you've had a social media post or photo removed and not understood why, then a new site wants to hear from you.
A project called Online Censorship is calling on people to report things that have been taken down.
Co-founder Jillian York told Newsbeat she wants "greater transparency" from social networks.
"We think it's important that they be transparent about what types of speech they do and don't allow, and what kind of content they take down."
The examples of "censorship" listed by the site include the case of Rupi Kaur, whose photo showed blood on her tracksuit bottoms during her period (the site later apologised and said it was an error).
Another case is the controversial 2012 anti-Islam film Innocence of Muslims, which was uploaded to YouTube but then blocked in a number of countries after it sparked riots.
People who want to report blocked content can answer a series of questions on the Online Censorship website.
"We will use that data to present more detail about how companies are censoring content," according to Jillian.
"We're going to use it to conduct analyses so we can see the different ways that different companies treat speech, or whether that's treated differently across different countries and so on."
Newsbeat contacted Facebook (which owns Instagram), Google (which owns YouTube), Twitter and Yahoo (which owns Flickr) for a response.
The company says the rules are designed to make users feel safe when using the sites.
It also explains that there are dedicated teams to respond to reports from users (and governments) about anything that may violate Facebook standards or local laws.
Google pointed us to this blog post, which says: "We have a bias in favour of free expression.
"Not just because it's a key tenet of free societies, but also because more information generally means more choice, more power, more economic opportunity and more freedom for people."
But Google also recognises there are limits, which are sometimes obvious but other times complicated "because our products are available in numerous countries with widely varying laws and cultures".
A Twitter spokesperson told us: "Twitter is committed to operating in an open and transparent manner when responding to government requests and copyright claims."
It added that these are published in its transparency report, which comes out twice a year.
"Additionally, we disclose actioned takedown requests in real time to Lumen, so our users can see the primary document and source of the request."
We've not yet had a response from Yahoo.
The Online Censorship project has been going since 2012 and was started by Jillian and fellow activist Ramzi Jaber.
The website has just relaunched thanks to a funding grant.
"I think these companies do have good intentions," Jillian says. "There are lots of types of content that they want to protect users from and that's reasonable.
"But at the same time I don't agree with them that their rules are always very clear."