As a (former) reporter, site monitoring is a big part of what I do on a daily basis and I used many, many such services.

I can attest that, at least from the landing page, this seems to be a very good execution of the concept, especially the text-based diffing to easily spot what changed and, most importantly, how.

The biggest hurdle for such apps however are 'js-based browser-rendered sites' or whatever they're called nowadays. How does Site Spy handle such abominations?

I like https://github.com/dgtlmoon/changedetection.io for this. Open source and free to run locally or use their Saas service.

    <?xml version='1.0' encoding='UTF-8'?>
    <rss xmlns:atom="http://www.w3.org/2005/Atom" xmlns:content="http://purl.org/rss/1.0/modules/content/" version="2.0"><channel><title></title><link>https://changedetection.io</link><description>Feed description</description><docs>http://www.rssboard.org/rss-specification</docs><generator>python-feedgen</generator><lastBuildDate>Thu, 12 Mar 2026 10:10:10 +0000</lastBuildDate></channel></rss>

Kudos for the launch. Super useful for people tracking granular updates!

I've built something similar for the startup I'm working at, but across the web with a Natural Language Interface: https://parallel.ai/products/monitor. It can find diffs in previous content or find new pages pertaining to the query depending on the semantics. Hope people on this thread are able to derive value from it.

Will this work on websites that may have Cloudflare captchas popping from time to time?

Nobody has mentioned, that FreshRSS [0] has built-in web scraper too. It is also easier to use (little bit, imho), than changedetection.io. Works like a charm for me - mostly window shoping thrift shops.

[0](https://freshrss.org/)

Does anyone here remember WinerWatch? The tool Mark Pilgrim wrote, that monitored changes to blog posts by (the notoriously trollish) Dave Winer? It caused a big stir in the blogosphere in 2003, and Mark took it down very quickly after public blowback. I always thought it was pretty cool and he should have left it up.

One of the very few surviving posts on the matter: https://burningbird.net/forget-the-law-forget-the-technology...

Calls to mind a long forgotten, and perhaps one of the most useful bash scripts I've written which addressed this issue in a very rudimentary way; Curl a url, hash the result to file, compare the current hash to the saved hash from the previous run and generate an email on diff.

My goal was to monitor the online release of tickets for the 2009 Scion Rock fest (luckily no js, or even Adobe Flash[!] in use), and it worked brilliantly to that end.

[grammar]

RSS is a useful interface, but: "Do most people just want direct alerts?" Yes, of course. RSS is beloved but niche. Depends who your target audience is. I personally would want an email, because that's how I get alerts about other things. RSS to me is for long form reading, not notifications I must notice. The answer to any product question like this totally depends on your audience and their normal routines.

Quick feedback:

1. RSS is just fine for updates. Given the importance of your visa use-case, were you thinking of push notifications?

2. Your competition does element-level tracking. Maybe they choose XPath?

I have my own hobby RSS server built around the Google Reader API. Two of my plugins are pretty similar to what you described: one checks a page’s current state against the last saved version and publishes an entry if anything changed, the other is basically a CSS selector-based feed builder. Always good to see RSS content here, thanks for posting!

On your questions: some people prefer RSS, others email, and services exist to convert between the two in both directions. My own rule of thumb is email for things that need actual attention and RSS for everything that can wait. If you’re thinking about turning this into a service, supporting both would make sense since people are pretty split on this.

This is a very common use case, I myself hand-coded something similar 13 years ago [1]. Kudos for the choice of RSS!

[1] https://github.com/piero/WebDiff

Something I was planning on building but never got round - if anyone wants to do it then feel free to use this idea.

Lots of companies really have no idea what javascript is being inserted into their websites - marketing teams add all sorts of crazy scripts that don't get vetted by anyone and are often loaded dynamically and can be changed without anyone knowing.

A service that monitors a site and flags up when the code changes - even better if it actually scans and flags up malicious code.

This is cool. I'd use it to track when state wildlife agencies update their regulation pages — those change once a year with no announcement and I always miss it. Element-level tracking would be perfect for that vs watching the whole page. To answer your question: I'd want both RSS and direct alerts (email/push) depending on urgency.

That looks nice, I use the free plan of https://visualping.io for some software changelogs, RSS feeds are a paid feature. Will check this out.

Looks cool

Very good!

This is something that existed in the past and I used successfully, but services like this tend to disappear

With lots of people showing how Saas apps can be easily written these days, I'm not as interested in those articles, as people showing off new ideas of what I can do with these new found abilities. This is cool.

Love this - I had a similar idea years ago, specifically for looking at long-text privacy policies and displaying the `diff`... but obviously never built it.

What you've done here is that and so much more. Congrats!

There's also AnyTracker (an app) that gives you this information as push notifications: https://anytracker.org/

How might this tool work in terms of “archiving” a site? This is just something I was wondering given the recent change and controversy about archiving service sites on Wikipedia.

Cool stuff. You should make it OSS and ask a one time fee for it. I would run it on my own infra but pay you once(.com)

This is quite a lovely implementation. Congrats!

This is interesting, gonna try it on our next project! thumb up

Back in 2000 I worked for a company that was trying to turn something like this into the foundation for a search engine.

Essentially instead of having a bunch of search engines and AI spamming your site, the idea was that they would get a feed. You would essentially scan your own website.

As crawlers grew from an occasional visitor to an actual problem (an inordinate percent of all consumer traffic at the SaaS I worked for was bots rather than organic traffic, and would have been more without throttling) I keep wondering why we haven’t done this.

Google has already solved the problem of people lying about their content, because RSS feeds or user agent sniffing you can still provide false witness to your site’s content and purpose. But you’d only have to be scanned when there was something to see. And really you could play games with time delays on the feed to smear out bot traffic over the day if you wanted.

Buddy I love you!

I have wanted this for so long! My job relies on following many German laws, bureaucracy pages and the like.

In the long run I want specific changes on external pages to trigger pull requests in my code (e.g. to update a tax threshold). This requires building blocks that don't exist, and that I can't find time to code and maintain myself.

I currently use Wachete, but since over a year, it triggers rate limits on a specific website and I just can't monitor German laws anymore. No tools seem to have a debounce feature, even though I only need to check for updates once per month.

Interesting... added to bookmarks. Could come in handy in the future

Tool looks useful. But how is it that toggling between light/dark mode results in a multi-second freeze..? Scrolling drops frames, confirmed with dev tools.

Tested on m1 pro 2021 laptop and recent higher-end (4080, 14700k, etc) desktop. Same on both.

The fuck?

Great for opponent monitoring on political campaigns. We made an in-house version of this on Biden ‘20.

i love a good rss tool. Thanks for sharing

that's quiet good. will give a try congrat !