Unblocker

Links to academic papers in emails and on websites often point to the PDF of the paper. However, on sites like arXiv, I'd much rather be pointed to the HTML page. The index page is quick to load, and has meta-data not available in the PDF, such as the version history. I've given up trying to ask people not to deep-link to PDFs, and have instead written a browser extension to do what I want.

Install links: Firefox and Chrome

This Firefox/Chrome extension redirects links to PDFs on arXiv, JMLR, NIPS, OpenReview and PMLR to an HTML index page, unless you clicked on the link from the hosting site. The Firefox version also handles PDFs on ACM and Semantic Scholar. Examples:

• ACM (Firefox only): this pdf link redirects to this webpage
• arXiv: this pdf link redirects to this webpage
• bioRxiv: this pdf link redirects to this webpage
• JMLR: this pdf link redirects to this webpage
• NIPS: this pdf link redirects to this webpage
• OpenReview: this pdf link redirects to this webpage
• PMLR: this pdf link redirects to this webpage
• Semantic Scholar (Firefox only): this pdf link redirects to this webpage

I've given the extension a fairly generic name. The redirect rules are stored in a list at the top of the code, and can easily be added to. However, making this list updatable within the extension is unlikely to happen soon, partly because of time, partly because allowing any URL to be redirected opens up security issues.

Download

If you just want to use the extension as it is, get it from one of the official addon sites:

• Unblocker for Firefox

• Unblocker for Chrome

Alternatives

• arxiv-url-replacer a different Chrome extension for arXiv, with a GUI. Edits links in pages, instead of intercepting requests. A similar approach could be taken using TamperMonkey, which would immediately work in multiple browsers. It can be tricky to catch all links though.

• Allen.YL Lee points out that a bookmarklet could be used to escape from a PDF after the fact, and provides an example.

Hacking

The code is written as a WebExtension, originally for Firefox. Lots of it, but not everything, works in Chrome too. The extension could probably be made to work in some other browsers, perhaps with some tweaking. But not by me.

If you want to add to the redirect rules, you currently have to edit the source code. To run the extension from the source:

• Firefox: go to about:debugging and click "Load Temporary Add-on". Select either of the files in the src directory. See Mozilla's WebExtensions documentation for more details.

• Chrome: go to chrome://extensions check developer mode, click load unpacked extension and select the src directory. See Chrome's extension development getting started guide for more details. At the moment what I actually deploy is the version in tmp_chrome_version after running ./package.sh. At packaging time I remove handling of sites that don't work as intended in Chrome yet.

Pull requests providing new rules, fixes, or improvements are welcome, as are github issues (include example URLs demonstrating what you want). If proposing code, please check both of the following in both Firefox and Chrome:

• Requests for PDFs from external sites or the location bar are redirected.

• Each redirect ends up at an HTML page with a link to the PDF, and clicking that link does give the PDF.

I've found the Chrome documentation and API harder to work with than Firefox's. Also, to upload extensions, the Chrome webstore makes you pay to register as a developer, which is a turn-off for casual development.