Ajax – How to manually send HTTP POST requests from Firefox or Chrome browser

No. The HTML 5 spec mentions:

The method and formmethod content attributes are enumerated attributes with the following keywords and states:

The keyword get, mapping to the state GET, indicating the HTTP GET method. The GET method should only request and retrieve data and should have no other effect.

The keyword post, mapping to the state POST, indicating the HTTP POST method. The POST method requests that the server accept the submitted form's data to be processed, which may result in an item being added to a database, the creation of a new web page resource, the updating of the existing page, or all of the mentioned outcomes.

The keyword dialog, mapping to the state dialog, indicating that submitting the form is intended to close the dialog box in which the form finds itself, if any, and otherwise not submit.

The invalid value default for these attributes is the GET state

I.e. HTML forms only support GET and POST as HTTP request methods. A workaround for this is to tunnel other methods through POST by using a hidden form field which is read by the server and the request dispatched accordingly.

However, GET, POST, PUT and DELETE are supported by the implementations of XMLHttpRequest (i.e. AJAX calls) in all the major web browsers (IE, Firefox, Safari, Chrome, Opera).

It is up to the browser but they behave in similar ways.

F5 usually updates the page only if it is modified. Modern browsers sends Cache-Control: max-age=0 to tell any cache the maximum amount of time a resource is considered fresh, relative to the time of the request.

CTRL-F5 is used to force an update, disregarding any cache. Modern browsers sends Cache-Control: no-cache and Pragma: No-cache

If I remember correctly it was Netscape which was the first browser to add support for cache-control by adding Pragma: No-cache when you pressed CTRL-F5.

┌───────────┬──────────────┬─────┬─────────────────┬──────────────────────────────┐
│ Version 4 │      F5      │  R  │      CLICK      │ Legend:                      │
│2021 MAY 19├──┬──┬──┬──┬──┼──┬──┼──┬──┬──┬──┬──┬──┤ C = Cache-Control: no-cache  │
│           │  │S │C │A │A │C │C │  │S │C │A │A │C │ I = If-Modified-Since        │
│           │  │H │T │L │L │T │T │  │H │T │L │L │T │ M = Cache-Control: max-age=0 │
│           │  │I │R │T │T │R │R │  │I │R │T │T │R │ N = Not tested               │
│           │  │F │L │  │G │L │L │  │F │L │  │G │L │ P = Pragma: No-cache         │
│           │  │T │  │  │R │  │+ │  │T │  │  │R │+ │ - = ignored                  │
│           │  │  │  │  │  │  │S │  │  │  │  │  │S │                              │
│           │  │  │  │  │  │  │H │  │  │  │  │  │H │ With 'CLICK' I refer to a    │
│           │  │  │  │  │  │  │I │  │  │  │  │  │I │ mouse click on the browsers  │
│           │  │  │  │  │  │  │F │  │  │  │  │  │F │ refresh-icon.                │
│           │  │  │  │  │  │  │T │  │  │  │  │  │T │                              │
│           │  │  │  │  │  │  │  │  │  │  │  │  │  │ 1: Version 3.0.6 sends I     │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    and C, but 3.1.6 opens    │
│Brave 1.24 │M │CP│CP│- │- │M │CP│M │CP│CP│M │CP│CP│    the page in a new tab,    │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    making a normal request   │
│Chrome 1   │MI│MI│MI│- │- │MI│- │MI│MI│MI│MI│MI│N │    with only I.              │
│Chrome 6   │MI│CP│CP│- │- │MI│CP│MI│CP│CP│MI│- │N │ 2: Version 10.62 does        │
│Chrome 90  │M │CP│CP│- │- │M │CP│M │CP│CP│M │CP│CP│    nothing. 9.61 might do C  │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    unless it was a typo in   │
│Edge 90    │M │CP│CP│- │- │M │CP│M │CP│CP│M │CP│CP│    my old table.             │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤ 3: Opens the currernt tab in │
│Firefox 3.x│MI│- │CP│- │- │MI│CP│MI│CP│1 │M │MI│N │    a new tab, but does not   │
│Firefox 89 │M │- │CP│- │M │M │CP│M │CP│3 │M │M │3 │    refresh the page if it is │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    cached in the browser.    │
│MSIE 8, 7  │I │- │C │- │I │I │  │I │I │C │I │I │N │                              │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤                              │
│Opera 10, 9│C │- │- │2 │- │C │- │C │C │C │C │- │N │                              │
│Opera 76   │M │CP│CP│- │- │M │- │M │CP│CP│M │CP│CP│                              │
├───────────┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──────────────────────────────┤
│                    https://stackoverflow.com/a/385491/36866                     │
└─────────────────────────────────────────────────────────────────────────────────┘

Note about Chrome 6.0.472: If you do a forced reload (like CTRL-F5) it behaves like the url is internally marked to always do a forced reload. The flag is cleared if you go to the address bar and press enter.