I want to be alerted when there's a change to a web page

What tools are there so that I could be alerted when there's a change to a web page.
I'd like to receive instant notification.
Or as close as  possible.
Visualping.io is TOO EXPENSIVE for constant monitoring.  They just raised the prices exorbitantly.
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Lucas BishopClick TrackerCommented:
You could use KimonoLabs for this.  

Here's an example of someone who scrapes their Kickstarter campaign page and sounds an air horn every time the donation value changes.
Morgan CQACommented:

I'm quite a fan of The Page Monitor app for Chrome which has real time notifications:


brothertruffle880Author Commented:
BAD NEWS.  That app is merging with the now insanely expensive Visual Ping.io. and clicking the link will take you to Visualping.io.
Morgan CQACommented:
Bummer! I had not realized that. Thanks for pointing that out.
brothertruffle880Author Commented:
VisualPing.io jacked up their rates MASSIVELY!!!      Apparently, they're the only ones now providing this service.
Ray PaseurCommented:
Their pricing seems to be in the range of a cup of coffee or a restaurant meal, which is hardly what I would call "massive," but that aside, what site(s) do you want to monitor?  The reason I ask is because different technologies will require different monitoring techniques.

One simple way you can do this sort of thing is with a message digest.  Simply read the page and take the PHP md5() checksum of the parts you want to monitor.  This may work well for static pages that are not timestamped.  If your pages change frequently but without any meaningful changes in content, then the visualping.io algorithms may be worth the value proposition to help avoid false positives.  Another possible issue would be the pages that are loaded via AJAX requests, where the valuable material in the web page is not present in the HTML but is built dynamically and inserted by JavaScript.  Screen "scrapers" will see only the HTML document, not the visual representation that appears on the client browser.

So please tell us a little more about what you're really looking for, and maybe we can suggest some more concrete ideas.
Bernard S.CTOCommented:
Assuming your page content is mostly html (no inserted ads etc) you might have a look at http://changedetection.com

I have been using their service for years,
I don't rememeber if the check/alert interval is smaller than daily.

I am also using the (commercial) service of http://monitis.com , but if you just want to monitor one site you will probably be happy with their free service. Note that they do not monitor changes, but online status and some keywords you define as a mandatory content
zzynxSr. Software engineerCommented:
I use both trackengine.com and watchthatpage.com.
However as far as I know checking on a daily base is the closest you can get to instant notification with these services.

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brothertruffle880Author Commented:
Here's the page I want to be alerted on.  

The classes are taught by great instructors and when they teach on a desirable day-of-week and time-of-day, the courses can sell out in minutes.

RSS Feed is okay but sometimes you can still get shut out.  Ditto twitter feeds.
The above page is the FIRST place a new course is listed.

If someone decides to drop out of the course there's an opening and it's reflected on the above page.  And it is NOT reflected anywhere else.
Lucas BishopClick TrackerCommented:
I'm not sure if you had a chance to look at the kimonolabs link I posted previously. It will do what you're looking for. You can setup an API that checks this page for updates every 15 minutes and emails you of changes:

1. Install [url="https://www.kimonolabs.com/learn/chrome-extension

kimonolabs add-on for chrome[/url]"]

2. Open the page you want to monitor http://losangeles.ucbtrainingcenter.com/courses/open

3. Launch the Kimonolabs toolbar icon

4. Click on the 'Click here to Register' text on the page and click the checkmarks next to every one of these selections:

kimono property

5. Click Done

6. Name it something (ie. class finder) on the next page and set the crawl for every 15 minutes

7. View [url="https://www.kimonolabs.com/apis/8duhmra8

your new API[/url] (shared link). The results should look similar to:"]class finder api

8. Go to the '[url="https://www.kimonolabs.com/apis/8duhmra8#use

use data[/url]' tab and set up email alerts for anytime this data changes."]
This should cover all your bases. If you want 'real-time' alerts (instead of every 15 minutes), you'd need to subscribe to a plan.
brothertruffle880Author Commented:
Hi Ray:
Yes.  You correct.  per "check" it's not expensive. But I'm asking for a "check" every five minutes.   So, when I use VisualPing.io every five minutes from 9 AM to 10 PM (hours of their registrar) seven days a week.  That's when it adds up.   Another upset is that they hiked their prices without any warning about a month ago.
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