First of all, it depends on what operating system you're using.
On Windows
If you right click and press "save" (Alternatively use ctrl-s) and then chose the file format "json" when saving.
On macOS
You can do this in a few ways, I'd suggest using curl. You'd do this by opening the terminal and navigating to the directory you'd like to download the file to. Then enter the following:
curl https://somedomain.com/somepath.json > fileName.json
This will download the file in its original format.
Answer from Maximilian on Stack OverflowVideos
First of all, it depends on what operating system you're using.
On Windows
If you right click and press "save" (Alternatively use ctrl-s) and then chose the file format "json" when saving.
On macOS
You can do this in a few ways, I'd suggest using curl. You'd do this by opening the terminal and navigating to the directory you'd like to download the file to. Then enter the following:
curl https://somedomain.com/somepath.json > fileName.json
This will download the file in its original format.
In a Mac, the curl solution proposed above doesn't work if the url isn't public (on my side I got this permissions error: unauthorized permission requested.
So, here's an alternative that worked for me. Using the Chrome browser, go to the url with the json, then right click, then 'Inspect'. That brings up the Chrome devtools ui. From there go to 'Sources' and you will see the json file in the list. Then right click and you will be able to click 'Save as'. This will then download the file to wherever you want!

UPDATE: In case this method doens't work (I realise it doesn't work in all cases), then simply copy-paste the text of the json into a text editor, and save the file with the json extension.
JSONView for chrome
- In-browser viewer
- Expand and contract JSON items
- Format validation
- Doesn't require .json ending
Enable:
Chrome wrench button >> Tools >> Extensions >> "Allow access to file URLs"
I got impatient waiting for a new Chrome API and ported JSONView just using simple regex matching.
http://github.com/jamiew/jsonview-chrome
This is a rough draft, but it works! You can install it using "Load unpacked extension" from the chrome://extensions -- working out some kinks but will package it as a real extension soon.
For further prettification checkout the "XML Tree" extension (SuperUser won't let me post 2 links yet)
For a lot of people, disabling the FastestChrome Extension solved the search.json problem.
source
This seems like a Google Instant bug -- clearing the cookies solved the problem for me. In Chrome, be sure to clear the cookies from "The beginning of time" rather than just the past hour.