| Mistake | Why it fails | |---------|---------------| | Double-encoding – file:/// → file%3A%2F%2F%2F → file%253A%252F%252F%252F | Browser tries to decode twice | | Using fetch() on an offline HTML file ( index.html opened from disk) | Origin null , CORS blocks fetch(file:///) | | Copy-pasting a file path from Windows Explorer ( C:\data.txt ) without converting to file:///C:/data.txt | Invalid URI format | | Expecting fetch('file:///etc/passwd') to work in a public website | Security policies explicitly forbid this |
: As noted in security write-ups on Cyber Security Write-ups , using extra slashes or alternative IP representations can trick the server into ignoring its safety rules. 2. Implementing the Fetch Request fetch-url-file-3A-2F-2F-2F
Are you trying to in a script, or are you looking for the correct syntax to load a local file? Using the Fetch API - MDN Web Docs | Mistake | Why it fails | |---------|---------------|
The fetch() method can technically use the file scheme if the resource is local. However, most modern browsers block fetch requests to file:/// from a web context for security reasons (CORS policy). Using the Fetch API - MDN Web Docs