* If `TRANSMISSION_WEB_HOME` is set, Transmission will look there for the [Web Interface](Web-Interface.md) files, such as the JavaScript, HTML, and graphics files.
* If `TR_CURL_SSL_NO_VERIFY` is set, Transmission will not validate SSL certificate for HTTPS connections when talking to trackers. See CURL's documentation ([CURLOPT_SSL_VERIFYHOST](https://curl.se/libcurl/c/CURLOPT_SSL_VERIFYHOST.html) and [CURLOPT_SSL_VERIFYPEER](https://curl.se/libcurl/c/CURLOPT_SSL_VERIFYPEER.html)) for more details.
* If `TR_CURL_VERBOSE` is set, debugging information for libcurl will be enabled. More information about libcurl's debugging mode [is available here](https://curl.haxx.se/libcurl/c/curl_easy_setopt.html#CURLOPTVERBOSE).
* If `TR_DHT_VERBOSE` is set, Transmission will log all of the DHT's activities in excruciating detail to standard error.
* If `TRANSMISSION_WEB_HOME` is _not_ set, non-Mac platforms will look for the [Web Interface](Web-Interface.md) files in `XDG_DATA_HOME` and in `XDG_DATA_DIRS` as described in [the XDG Base Directory Specification](https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html#variables). `XDG_DATA_HOME` has a default value of `$HOME/.local/share/`.
* If `TRANSMISSION_HOME` is _not_ set, Unix-based versions of Transmission will look for their settings in `$XDG_CONFIG_HOME/transmission/`. `XDG_CONFIG_HOME` has a default value of `$HOME/.config/`.
2. If `TRANSMISSION_HOME` is _not_ set, Mac-based versions of Transmission will look for their settings in `$HOME/Library/Application Support/Transmission`.
* Transmission uses the [libcurl](https://curl.haxx.se/libcurl/) library for HTTP- and HTTPS-based tracker announces and scrapes. Transmission does not support proxies, but libcurl itself honors [a handful of environment variables](https://curl.haxx.se/libcurl/c/curl_easy_setopt.html#CURLOPTPROXY) to customize _its_ proxy behavior.