There is a long standing problem with Vivaldi not adding every kind of search engines, e.g. the current implementation still does not add search engines like SearX

This happens because those engines use POST instead of GET in their search forms and Vivaldi does not (yet) check for that.

To mitigate the problem …

… you can use the following bookmarklet:

javascript:(function()%7Bvar%20x,i%3Bx%3Ddocument.forms%3Bfor(i%3D0%3Bi%3Cx.length%3B++i)x%5Bi%5D.method%3D%22get%22%3Balert(%22Changed%20%22%20+%20x.length%20+%20%22%20forms%20to%20use%20the%20GET%20method.%5Cn%5CnDON'T%20USE%20THE%20ALTERED%20PAGE%20NOW!%5Cn%5Cn%20-%20Right-click%20in%20the%20search%20field%5Cn%20-%20select%20%5C%22Add%20as%20search%20engine%5C%22%5Cn%20-%20Open%20%5C%22Settings%5C%22%20%3E%20%5C%22Search%5C%22%5Cn%20-%20Click%20the%20edit%20button%20for%20the%20new%20search%5Cn%20-%20Check%20%5C%22Use%20Post%5C%22%5Cn%5CnEnjoy!%22)%3B%7D)()%3B

• Create a new bookmark in the panel and copy/paste the line above in the URL field of the Bookmarks panel.
• Give it a name like e.g. “GET the POST search”.
• Optional add a shortcut like “getit” too.

Now you can go to one of the search engine result pages 1), e.g. the one linked above and either click on the bookmarklet or type the shortcut in the URL bar and hit enter.

An alert-box with additional instructions will pop up. Follow the instructions.

Warning: The site will be altered by the bookmarklet. Don’t use it for a search before you have reloaded the page or else it might break!

1) It might not work if you try it on the start page of the search engine. In this case search for “test” and try applying the bookmarklet on the result page. Some search engine still might not work that way because they use other means and time based searches, but the majority should work just fine.

How it works

The bookmarklet changes all FORM elements on the page to use GET instead of POST. This allows right click > “Add as Search Engine” to detect it and enter the corresponding values it needs. Don’t forget to set the “Use POST Method” checkbox for the newly created search in “Vivaldi > Settings > Search”.

Here the decoded and unminified “source code”:


javascript: (function () {
var x, i;
x = document.forms;
for (i = 0; i < x.length; ++i) {
x[i].method = "get";
}
alert("Changed " + x.length + " forms to use the GET method.\n\nDON'T USE THE ALTERED PAGE NOW!\n\n - Right-click in the search field\n - select \"Add as search engine\"\n - Open \"Settings\" > \"Search\"\n - Click the edit button for the new search\n - Check \"Use Post Method\"\n\nEnjoy!");
})();

If the search engine does not use POST …

…but “Add as Search Engine …” entry still does not want to show up, see Adding Search Engines to the Vivaldi Browser (followup)