Website Change Detection

I recently encountered a work-related scenario in which I felt that it would be beneficial for me to know when a website had been updated. The website in question performs periodic updates of certain kinds of data in a downloadable file format, but it does not offer a notification mechanism (e.g., via email, RSS, or other technology) when such changes occur. That led me to explore options for website change detection.

There appear to be many options available, but I found that most of them required subscriptions. Because I am merely evaluating these technologies, I was only looking for free options. That led me to sign up for accounts at Visualping and PageMonitor. I configured both of them to monitor my blog, https://digitaldaddyla.blogspot.com/.

Visualping and PageMonitor use slightly different methods to determine if a change has occurred. For Visualping, setting up a new monitor requires entering the URL and specifying either an AI prompt to describe what changes you are looking for or “Any changes” which they label as “No AI used” as depicted below. I used the “Any changes” option. I also had the option to specify the frequency of page checks, and I chose “every day”. It did not allow me to specify an exact time.

For PageMonitor, setting up a task requires that you specify a URL to display the current webpage. From there, you specify both an “Anchor area” and “Region of interest” by drawing boxes around both regions. The region of interest is the part of the page you want to monitor. The anchor area is a reference point that is used to relocate the region of interest each time the page is checked—this should be an area of the page that is not expected to change. You then specify how often to run the task. When I chose “once a day”, it prompted me to enter a time, for which I think I chose 7 AM.

I have since published 7 new blog entries and have been receiving email notifications from both Visualping and PageMonitor. For the purpose of this blog post, I am presenting my findings based on review of change logs in each of my accounts. Here is a summary.

I have several observations. First, I noticed that Visualping failed to detect my most recent blog post on 4/17/2026, while PageMonitor has not missed any new blog posts. It is not clear to me why Visualping did not detect the 4/17/2026 blog post. One possibility is that I have not logged in to my account since setting up the monitoring job. I received an email from Visualping on 5/2/2026 that stated, “We have not seen you for 3 months! We would like to confirm that you are still interested in us checking things for you. Please login in the next 3 days to keep your current monitoring frequency. Otherwise, your job frequency will be reduced to checking only once a month.” However, my monitoring frequency would have to have been reduced prior to 4/17 to explain the false negative.

Second, the elapsed time between blog publication and webpage change detection was generally 1 day for both Visualping and PageMonitor. However, there was one blog post (Chicken Al Pastor and Oxford Commas) which was not detected by Visualping until after 2 days.

Third, Visualping seems to detect website changes at different hours of the day, while PageMonitor allowed me to specify exactly what time to run my daily task. Notice that the transition from 7:01 AM to 8:01 AM can be explained by Daylight Saving Time beginning on Sunday 3/8/2026.

My final observation is that PageMonitor occasionally alerted me to changes to my blog when I didn’t make any. For example, the “3D Printing Without Wi-Fi” blog that I published on 2/13/2026 was correctly detected on 2/14/2026. However, PageMonitor detected changes on 2/25/2026 and 2/26/2026. I suspect that maybe an image did not load on 2/25 which resulted in a conclusion that the page appeared different, and then the image properly loaded on 2/26 which resulted in another conclusion that the page changed again.

Another example of a false positive from PageMonitor is from my “3D Printing and Firearm Blocking Technology” blog post on 4/17/2026. Following a successful detection on 4/18/2026, it falsely detected a change on 4/29, errored out on 4/30, and falsely detected another change on 5/1, even though I did not make any edits to the blog post or publish any new blogs.

In conclusion, based on a small sample size, Visualping appears to err on the side of false negatives, and PageMonitor seems to err on the side of false positives. It is possible that some of these errors could be due to webpage itself (e.g., images not loading). In any case, I find both Visualping and PageMonitor to be useful for detecting changes to websites. If you are looking for free options, I would recommend checking out both of them.