TL;DR – The app still works but the block list has not been updated since 2018-10-20.
I’ve had the Purify App installed on my iOS devices since it was originally released and have recently been wondering if it still worked. The last version update for the App was 2018-09-21 which honestly is probably fine since blocking content in a web browser is probably a solved problem at this point and all that really matters is that the block list itself is being updated.
When you launch Purify on your device and click ‘Update Now’ it appears to be checking and pulling the latest block list right? I had assumed so.
Today I decided to check. I grabbed a copy of mitmproxy, installed it’s SSL certificate on a test device and started poking around. Here is what I found.
When you click the ‘Update Now’ button the App reaches out to: https://www.purify-app.com/app-services/latest-version?1667683942.93690300313600ACFB
The first number (1667683942) is a Unix timestamp for right now. I have no idea what the second number and characters (93690300313600ACFB) is for. It changes every time I click ‘Update Now’.
Either way you don’t need either value to view the contents of https://www.purify-app.com/app-services/latest-version which is just a text file named “latest-version” that contains a number (105 as of this writing).
The number 105 signifies the latest revision of the block list Purify uses. If you already have this version download the Purify App does nothing further.
Using mitmproxy I was able to intercept and alter the response from the web server so that it returned “106” instead of “105” which triggered the App into thinking there was a new block list to download. I then had what I was after which was the URL of the block list itself.
The 105 version of the block list can be found here: https://www.purify-app.com/app-services/blockerList.105.json
If you change 105 to 104 you’ll get a previous version of the block list.
Checking the headers on the web request I found the “last-modified” stated “Sat, 20 Oct 2018 17:35:43 GMT”.
Last-Modifiedresponse HTTP header contains a date and time when the origin server believes the resource was last modified.
This leads me to believe the block list for Purify hasn’t been updated since 2018-10-20 making the App fairly useless at this point despite likely still functioning.
Before publishing this blog post I reached out to the author for comment but heard nothing back after waiting a week.
If you’ve somehow stumbled across this blog post before purchasing Purify, I’d recommend spending your $1.99 elsewhere. It’s a little disappointing the developer hasn’t pulled the App from the store where it can still be purchased or published anything on the official Website or Twitter feed stating the block list is no longer being updated.
Do I have a recommendation for an alternative? Not an iOS App specifically. I use a PiHole personally.