Two different locks, and people arrive expecting the wrong one
"Locked PDF" means two unrelated things, and which one you have decides whether this takes two seconds or is impossible.
Restrictions. The document opens for anybody, with nothing to type, but the reader greys out printing or refuses to let you copy text. The file is encrypted with an empty password, so any reader can decrypt it, and it separately carries a set of flags asking readers to forbid things. No password is needed to take those off. This is the common one, and it is what bank statements, supplier drawings and pay slips usually have.
A password to open. The document will not open at all. That is real encryption, and the password is the only way in.
Drop your file in and it says which one it is looking at before you do anything.
How this tool works
When you drop a file in it is opened to see which kind of lock is on it, before you are asked for anything. A file that opens but reports restrictions is one case; a file that refuses to open at all is the other.
The engine is qpdf, the reference tool for this, compiled to run in the browser and downloaded from this site when you use the tool. The document is decrypted rather than redrawn, so every page stays exactly as it was.
Then the finished file is reopened and inspected, and what it reports about printing, copying and editing is read back off the result rather than assumed. "Unlocked" is easy to claim, and a tool that removed the password but left the restrictions would look identical up to the moment you needed it.
If you do not have the password, nothing honest can help
Worth being blunt about, because it is the most common reason people land on a page like this.
A password-protected PDF is encrypted with AES. Without the password there is no clever trick, no header to edit and nothing to strip: the content is not there in readable form at all. This tool asks for the password because it genuinely needs it.
Sites promising to open one anyway are doing one of two things. They are guessing, which works on "password1" and on nothing else. Or they are exploiting 40-bit RC4, the broken mode from the 1990s, which does fall over in seconds and which almost nothing has used for twenty years.
If it is your own document, the password is usually recoverable from wherever you saved it, or from whoever sent it. That is the real answer and it is a better one than a service that wants your file uploaded.
So this one runs in your browser
A locked PDF is, by definition, a document somebody thought was worth locking. Uploading it to a stranger's server to have the lock taken off is a strange thing to do, and uploading the password with it is stranger.
Nothing here leaves your machine. The engine is a build of qpdf, the reference tool for this, compiled to run in the browser. It downloads once, when you use the tool, from this site rather than from somebody else's.
The pages are not touched
The document is decrypted, not rebuilt. Text stays selectable and searchable, drawings stay vector, form fields survive, and the file stays roughly the size it was.
That is worth checking elsewhere. A tool that rasterises to unlock hands you back a stack of pictures: it looks the same, and the text can never be searched or copied again.
Use it on your own documents
This removes protection when you have the right to remove it, which covers your own files and anything you have been given the password for. It is not a way into somebody else's document and it will not work as one.
Common questions
How do I remove a password from a PDF?
Drop it in. If it opens for you already and only carries restrictions, they come off with no password at all. If it needs a password to open, type the one you have and it comes off permanently. Nothing is uploaded and the password is not stored.
Can it open a PDF when I do not know the password?
No, and nothing honest can. A password-protected PDF is properly encrypted, so without the password there is nothing to work with. Anything claiming otherwise is either guessing at common passwords or relying on the broken 40-bit mode from twenty years ago.
Why can I open this PDF but not print or copy from it?
Because it carries restrictions rather than a password. The document is encrypted with an empty user password, so any reader can open it, and the file separately asks readers to forbid printing or copying. Removing that needs no password and is what this does.
Is my password sent anywhere?
No. The whole job runs on this page using your own machine, so the file and the password both stay with you. You can confirm it in your browser network tab.
Does unlocking damage the document?
No. It is decrypted rather than redrawn, so every page stays exactly as it was. Text stays selectable and searchable, drawings stay vector and stay sharp, and the file stays roughly the size it was.