By default, `fetchurl` uses `"recursive"` mode when the `executable` attribute is set to `true`, so you don't need to specify `recursiveHash` in this case.

  _Default value:_ `false`.

`executable` (Boolean; _optional_)
: If `true`, sets the executable bit on the downloaded file.

  _Default value_: `false`.

`downloadToTemp` (Boolean; _optional_) []{#sec-pkgs-fetchers-fetchurl-inputs-downloadToTemp}
: If `true`, saves the downloaded file to a temporary location instead of the expected Nix store location.
  This is useful when used in conjunction with `postFetch` attribute, otherwise `fetchurl` will not produce any meaningful output.

  The location of the downloaded file will be set in the `$downloadedFile` variable, which should be used by the script in the `postFetch` attribute.
  See [](#ex-fetchers-fetchurl-nixpkgs-version-postfetch) to understand how to work with this attribute.

  _Default value:_ `false`.

`postFetch` (String; _optional_)
: Script executed after the file has been downloaded successfully, and before `fetchurl` finishes running.
  Useful for post-processing, to check or transform the file in some way.
  See [](#ex-fetchers-fetchurl-nixpkgs-version-postfetch) to understand how to work with this attribute.

  _Default value:_ `""`.

`netrcPhase` (String or Null; _optional_)
: Script executed to create a {manpage}`netrc(5)` file to be used with {manpage}`curl(1)`.
  The script should create the `netrc` file (note that it does not begin with a ".") in the directory it's currently running in (`$PWD`).

  The script is executed during the setup done by `fetchurl` before it runs any of its code to download the specified content.

  :::{.note}
  If specified, `fetchurl` will automatically alter its invocation of {manpage}`curl(1)` to use the `netrc` file, so you don't need to add anything to `curlOpts` or `curlOptsList`.
  :::

  :::{.caution}
  Since `netrcPhase` needs to be specified in your source Nix code, any secrets that you put directly in it will be world-readable by design (both in your source code, and when the derivation gets created in the Nix store).

  If you want to avoid this behaviour, see the documentation of `netrcImpureEnvVars` for an alternative way of dealing with these secrets.
  :::

  _Default value_: `null`.

`netrcImpureEnvVars` (List of String; _optional_)
: If specified, `fetchurl` will add these environment variable names to the list of [impure environment variables](https://nixos.org/manual/nix/stable/language/advanced-attributes.html#adv-attr-impureEnvVars), which will be passed from the environment of the calling user to the builder running the `fetchurl` code.

  This is useful when used with `netrcPhase` to hide any secrets that are used in it, because the script in `netrcPhase` only needs to reference the environment variables with the secrets in them instead.
  However, note that these are called _impure_ variables for a reason:
  the environment that starts the build needs to have these variables declared for everything to work properly, which means that additional setup is required outside what Nix controls.

  _Default value:_ `[]`.

`curlOpts` (String; _optional_)
: If specified, this value will be appended to the invocation of {manpage}`curl(1)` when downloading the URL(s) given to `fetchurl`.
  Multiple arguments can be separated by spaces normally, but values with whitespaces will be interpreted as multiple arguments (instead of a single value), even if the value is escaped.
  See `curlOptsList` for a way to pass values with whitespaces in them.

  _Default value:_ `""`.

`curlOptsList` (List of String; _optional_)
: If specified, each element of this list will be passed as an argument to the invocation of {manpage}`curl(1)` when downloading the URL(s) given to `fetchurl`.
  This allows passing values that contain spaces, with no escaping needed.

  _Default value:_ `[]`.

`showURLs` (Boolean; _optional_)
: If set to `true`, this will stop `fetchurl` from downloading anything at all.