[HN Gopher] Show HN: I built a tool that watches webpages and ex...
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Show HN: I built a tool that watches webpages and exposes changes
as RSS
I built Site Spy after missing a visa appointment slot because a
government page changed and I didn't notice for two weeks. It
watches webpages for changes and shows the result like a diff. The
part I think HN might find interesting is that it can monitor a
specific element on a page, not just the whole page, and it can
expose changes as RSS feeds. So instead of tracking an entire
noisy page, you can watch just a price, a stock status, a headline,
or a specific content block. When it changes, you can inspect the
diff, browse the snapshot history, or follow the updates in an RSS
reader. It's a Chrome/Firefox extension plus a web dashboard.
Main features: - Element picker for tracking a specific part of a
page - Diff view plus full snapshot timeline - RSS feeds per
watch, per tag, or across all watches - MCP server for Claude,
Cursor, and other AI agents - Browser push, Email, and Telegram
notifications Chrome:
https://chromewebstore.google.com/detail/site-spy/jeapcpanag...
Firefox: https://addons.mozilla.org/en-GB/firefox/addon/site-spy/
Docs: https://docs.sitespy.app I'd especially love feedback on two
things: - Is RSS actually a useful interface for this, or do most
people just want direct alerts? - Does element-level tracking feel
meaningfully better than full-page monitoring?
Author : vkuprin
Score : 126 points
Date : 2026-03-11 16:21 UTC (6 hours ago)
(HTM) web link (sitespy.app)
(TXT) w3m dump (sitespy.app)
| makepostai wrote:
| This is interesting, gonna try it on our next project! thumb up
| pwr1 wrote:
| Interesting... added to bookmarks. Could come in handy in the
| future
| enoint wrote:
| 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?
| vkuprin wrote:
| Yep, Site Spy already has push notifications, plus email and
| Telegram alerts. I see RSS as the open interface for people who
| want to plug updates into their own reader or workflow. For
| urgent things like visa slots or stock availability, direct
| alerts are definitely the main path.
|
| And yeah, element-level tracking isn't a brand new idea by
| itself. The thing I wanted to improve was making it easy to
| pick the exact part of a page you care about and then inspect
| the change via diffs, history, or RSS instead of just getting a
| generic "page changed" notification
| xnx wrote:
| I like https://github.com/dgtlmoon/changedetection.io for this.
| Open source and free to run locally or use their Saas service.
| vkuprin wrote:
| Yep, changedetection.io is a good project. With Site Spy, I
| wanted to make the browser-first workflow much easier: install
| the extension, connect it to the dashboard, click the exact
| part of the page you care about, and then follow changes as
| diffs, history, or RSS with very little setup. I can definitely
| see why the open-source / self-hosted route is appealing too.
| xnx wrote:
| Changedetection has an extension too: https://chromewebstore.
| google.com/detail/changedetectionio-w...
| raphman wrote:
| There's also https://github.com/thp/urlwatch/ - (not aware of
| any SaaS offer - self-hosted it is).
| vkuprin wrote:
| Yep, urlwatch is a good one too. This category clearly has a
| strong self-hosted tradition. With Site Spy, what I'm trying
| to make much easier is the browser-first flow: pick the exact
| part of a page visually, then follow changes through diffs,
| history, RSS, and alerts with very little setup
| pelcg wrote:
| Looks cool and this can be self hosted and it is for free.
|
| Nice will try this out!
| beepbooptheory wrote:
| Sure but this one has a MCP server, costs money, and was
| presumably made last night!
| nicbou wrote:
| It's been around for a while and recommended by many. I tried
| it myself and it's okay.
| digitalbase wrote:
| 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)
| bananaflag wrote:
| Very good!
|
| This is something that existed in the past and I used
| successfully, but services like this tend to disappear
| vkuprin wrote:
| That's a completely fair concern. Services in this category do
| need to earn trust over time. I built the backend to handle a
| fair amount of traffic, so I'm not too worried about growth on
| that side. My goal is definitely to keep this running for the
| long term, not treat it like a one-off project
| tene80i wrote:
| 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.
| ikari_pl wrote:
| It's niche because some companies decided so.
|
| you used to have native RSS support in browsers, and latest
| articles automatically in your bookmarks bar.
| ctxc wrote:
| That's good reasoning, but the parent's point still stands?
| hinkley wrote:
| 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.
| deceptionatd wrote:
| Well-designed sitemaps and use of something like
| https://www.indexnow.org/ helps.
|
| Cloudflare has Crawler Hints which works well IME:
| https://blog.cloudflare.com/crawler-hints-how-cloudflare-is-...
| ahmedfromtunis wrote:
| 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?
| vkuprin wrote:
| Thanks, that's a really good question. Site Spy uses a real
| browser flow, so it generally handles JS-rendered pages much
| better than simple HTML-only polling tools. In practice, the
| trickier cases tend to be sites with aggressive anti-bot
| protection or messy login/session flows rather than JS itself.
| I'm trying to make those limitations clearer so people don't
| just hit a vague failure and feel let down
| dev_at wrote:
| There's also AnyTracker (an app) that gives you this information
| as push notifications: https://anytracker.org/
| Knork-and-Fife wrote:
| and also visualping.io which sends email alerts
| nicbou wrote:
| 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.
| vkuprin wrote:
| German laws and bureaucracy pages are exactly the kind of thing
| where tracking one specific part of a page is much more useful
| than watching the whole page. And yeah, more control over check
| frequency makes a lot of sense if monthly checks are enough and
| rate limits are the main problem. I'd be curious what kind of
| schedule would work best for you there?
| nicbou wrote:
| Monthly is fine, but not monthly _all at once_ , because I
| watch multiple pages on one website, and that triggers the
| rate limiting.
|
| The ideal pipeline for me would be "notice a change in a
| specific part of a page, use a very small LLM to extract a
| value or answer a question, update a constant in a file and
| make a pull request".
|
| I've been thinking about this pipeline for a long time
| because my work depends on it, but nothing like it seems to
| exist yet. I'll probably write my own, but I just can't find
| the time.
| iamflimflam1 wrote:
| 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.
| layman51 wrote:
| 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.
| vkuprin wrote:
| Site Spy keeps snapshot history, so you can revisit older
| versions of a page and inspect how it changed over time, not
| just get the latest alert. I'd describe it more as monitoring
| with retained history than as a dedicated public archive, but
| deeper archival integrations are definitely something I've
| thought about
| dogline wrote:
| 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.
| lkozloff wrote:
| 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!
| breadcat wrote:
| i love a good rss tool. Thanks for sharing
| docybo wrote:
| that's quiet good. will give a try congrat !
| butterlesstoast wrote:
| This is quite a lovely implementation. Congrats!
| plutokras wrote:
| 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.
| Hauk307 wrote:
| 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.
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(page generated 2026-03-11 23:00 UTC)