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Firefox Prevents Local Machine File Access But Firefox Dev Ed Allows It . . .

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  • 1 has this problem
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  • Last reply by tamjk

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Local Machine: Dell Inspiron i5-7200 / 16 GB RAM / Local Op Sys: Ubuntu 20.04LTS

Firefox version: 99.0 FFDE version: 100.0b5

Node.js version 14.18.1 npm version 6.14.15


I had a Node.js web app running on my local machine all usual browsers like Firefox, Firefox Dev Ed (FFDE), Chromium, Edge, Opera, etc till recently.

Recently it shows an error when run on Firefox (also on Chromium, Opera and Edge) although continuing to run okay on FFDE.

Firefox Error: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at file:///home/sandbar/Desktop/nodeapp-local/undefined. (Reason: CORS request not http).

Edge Error: Access to XMLHttpRequest at 'file:///home/sandbar/Desktop/nodeapp-local/undefined' from origin 'null' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, chrome-extension, edge, https, chrome-untrusted.


Naturally, I need to test the web app on my local machine using several browsers before I should upload it to a server and trial it there.

So how do I configure the browser and/or app to allow access to local machine files ?

''' Local Machine: Dell Inspiron i5-7200 / 16 GB RAM / Local Op Sys: Ubuntu 20.04LTS Firefox version: 99.0 FFDE version: 100.0b5 Node.js version 14.18.1 npm version 6.14.15''' I had a Node.js web app running on my local machine all usual browsers like Firefox, Firefox Dev Ed (FFDE), Chromium, Edge, Opera, etc till recently. Recently it shows an error when run on Firefox (also on Chromium, Opera and Edge) although continuing to run okay on FFDE. Firefox Error: ''Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at file:///home/sandbar/Desktop/nodeapp-local/undefined. (Reason: CORS request not http).'' Edge Error: ''Access to XMLHttpRequest at 'file:///home/sandbar/Desktop/nodeapp-local/undefined' from origin 'null' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, chrome-extension, edge, https, chrome-untrusted.'' Naturally, I need to test the web app on my local machine using several browsers before I should upload it to a server and trial it there. So how do I configure the browser and/or app to allow access to local machine files ?

Modified by tamjk

Chosen solution

Sorted.

The frontend JavaScript had an error in it after a recent update that sent the XHR to an undefined endpoint. It was this that triggered a CORS error in Firefox, not the fact that I was using a local server call.

Why FFDE showed no error was likely that the browser cache had not been cleared since the web app was last run on it. I can explain it no other way.

Anyway, after correcting the frontend request sending script - and taking care to close FF, clear the cache etc and restart FF - all ran well on both browsers.

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Chosen Solution

Sorted.

The frontend JavaScript had an error in it after a recent update that sent the XHR to an undefined endpoint. It was this that triggered a CORS error in Firefox, not the fact that I was using a local server call.

Why FFDE showed no error was likely that the browser cache had not been cleared since the web app was last run on it. I can explain it no other way.

Anyway, after correcting the frontend request sending script - and taking care to close FF, clear the cache etc and restart FF - all ran well on both browsers.

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That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.

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I see no Solved Problem button.

The Solution chosen text beside Undo button is non-clickable to me.

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