Mass monitoring round-trip flight prices using Google Flights

The most useful feature in Google Flights is this table called Date grid that shows you all the prices in a 7x7 grid - 7 days of outbound flights matched with 7 days of return flights. The priced shown are the cheapest round trip for that date pair. With this, I can monitor 49 round trip prices at once.

Assuming you have a target date range for your travel, you can then set your flights dates like this in Google Flights to control the Date grid boundaries.

Outbound flight: Earliest date plus 3 days, e.g. July 27 + 3 days = July 30

Return flight: Latest date minus 3 days, e.g. August 18 - 3 days = August 15

Now to monitor this and notify me when there are changes, I use this tool https://changedetection.io/ I self-host this for free but you can subscribe to their service for $9 a month.

This is how it looks like in ChangeDetection.io:

For my planned travel, I have target ranges of dates for both outbound and return, and I divide them into 7 day segments. I create unique URLs in Google flights manually for each of these target dates. Example is https://www.google.com/travel/flights/search?tfs=CBwQAhovagcIARIDQkVSagcIARIDUVBQEgoyMDIzLTA3LTIzcg0IAxIJL20vMDE5NXBkKAIaL2oNCAMSCS9tLzAxOTVwZBIKMjAyMy0wOC0xNXIHCAESA0JFUnIHCAESA1FQUCgCcAGCAQsI____________AUABQAFAAkACSAGYAQE&curr=EUR

Use this URL https://changedetection.io/share/YyFkaFF8brca when creating a new change detection watch and just update the URL in the edit screen to match your preferences.

There's a section "Trigger/wait for text" where you can input a regex that can detect if your target price has been reached. Mine is set at /€[1-2],[0-9][0-9][0-9]/ which means notify me when roundtrip tickets are between €1,xxx to €2,xxx.

After you've setup where to send the notifications, you can save the monitor and that's it.