Online file converter: Web-based tool or service that allows you to convert files from one format to another through the internet. Users upload a file in a specific format, it is converted on the site's server into a different format of their choice, without the need to install any software or applications on their device. Online file converters support a wide range of file types, including documents, images, videos, audio files, and more.

Let's assume for the sake of simplicity that we're talking about ethical online converters that don't collect/sell/share any information about the files uploaded by the users, so the file really makes a private round trip.

I'm wondering about the legal responsibility of these online converters, as they're essentially redistributing derivative work of pretty much anything you give them, whether or not you're allowed to modify them in the first place. The derivative work is downloaded from their servers at some point in time.

This question is a bit related to the issue of uploading copyrighted material to social media (with the Online Copyright Infringement Liability Limitation Act in the USA), except that the files here are only supposed to be downloaded by the same person who uploaded them (a private link is created and will expire quickly).

Additional assumptions (bonus):

  • What if a website detects that a lot of users upload the same files and implements a cache? The converted files would then be stored in the medium-long term, but still only privately accessible only by people who have the original file (and site owners). That would probably already be illegal in the UK but I don't know about EU or USA.
  • What if we have a cache and the files are encrypted with a hash of the source file, rendering their access practically impossible without the original, even for site owners?
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    As a practical matter, if nobody has access to the file but the user who uploaded the source and downloaded the converted result, the only person who could be demonstrably liable for violating any copyright in the source is the user.
    – phoog
    May 31, 2023 at 10:52
  • @phoog I didn't think of it from a practical PoV but you're right in this situation. That's pretty much how encrypted cloud storage services operates and it seems legal. Let's just hope that encryption isn't outlawed as some politicians would like to 😬 For anyone else stumbling on this post, I'm still curious to know how things would work for the original assumption, and when the file is cached without encryption, because that's what happens most of the time.
    – MrAnima
    May 31, 2023 at 11:25
  • I also found this USA ruling about Google Cache, saying that server-side caching is considered fair use given that the caching is triggered by a user action instead of being done eagerly. We could assume that cached pages are probably modified so that links/images also refer to their cached versions too, so they're also derivative work.
    – MrAnima
    May 31, 2023 at 11:36
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    "assume […] we're talking about ethical online converters that don't collect/sell/share any information about the files" So it's a purely hypothetical situation?
    – pipe
    May 31, 2023 at 21:04
  • 2
    Practically speaking, I don't see how one can send any file over the internet nowadays without totally transforming the binary representation of the file several times (at the sender, as it passes through third party networks, and at the destination). Any file must be packetized, which chops the file into small pieces and adds routing data, and if any encryption is involved completely transforming its representation. Furthermore, if the file system at the destination is not the same as at the source, then the file might not even be exactly the same bit-for-bit once its reassembled.
    – user4574
    Jun 1, 2023 at 5:17

1 Answer 1


Online file converters are legal: there is no law that prohibits a person from making a program available and executing online, including creating output in the form of a file. It is possible that some person may illegally copy copyright-protected material then use a website to modify that material, in which case the question of vicarious liability for copyright infringement could arise, so we appeal to the DMCA safe harbor provisions to see what the website must do. First, the owner of copyright must submit a properly constructed takedown notice to the website. Crucially, the notice must contain sufficient information that the website operator can find and take down the item(s) in question. Assuming that the complainant can supply the "where is it" information, then there is a notice and counter-notice routine where the uploader is informed and can deny the accusation – the website operator doesn't evaluate the merits of the claim, he only sees that the formalities were observed. If the operator follows the rules, he cannot be held vicariously liable.

If the link does not expire and if it is somehow promulgated, the technical potential for being a contributor to copyright infringement becomes very real, but it puts the operator in no worse a legal position than Youtube. So the question is not just related to OCILLA, it is entirely covered by that law. Questions of how users or website owners are "supposed to" act don't figure into this. If the website owner does not comply with those provisions, they have no access to the safe harbor provisions, and they can be sued. However, the website itself remains legally "permitted" (there never was a prohibition of such a website).

  • 1
    Thanks for the detailed answer. What you made me understand is that DMCA only cares about what's "observable" from the exterior. I expected some laws to care about how the data moves between actors (clients/server) or how it is stored (basically, things that are hidden from plain sight). Of course this wouldn't be practically enforceable without some government entity breaking into the server or a data leak occurring, but might still be technically outlawed.
    – MrAnima
    May 31, 2023 at 19:38

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