Chromium tweaks - ArchWiki

# Chromium tweaks

Related articles

- Chromium
- Firefox tweaks

## Browsing experience

### chrome://xxx

A number of tweaks can be accessed via typing chrome://xxx in the URL field. A complete list is available by typing chrome://chrome-urls into the URL field. Some of note are listed below:

- chrome://flags - access experimental features such as WebGL and rendering webpages with GPU, etc.
- chrome://plugins - view, enable and disable the currently used Chromium plugins.
- chrome://gpu - status of different GPU options.
- chrome://sandbox - indicate sandbox status.
- chrome://version - display version and switches used to invoke the active `/usr/bin/chromium`.

An automatically updated, complete listing of Chromium switches is available here.

### Broken icons in Download tab

If Chromium shows icon placeholders (icons representing broken documents) instead of appropriate icons in its Download tab, the likely cause is that the gnome-icon-theme package is not installed.

### Chromium overrides/overwrites Preferences file

If you enabled syncing with a Google Account, then Chromium will override any direct edits to the Preferences file found under `$HOME/.config/chromium/Default/Preferences`. To work around this, start Chromium with the `--disable-sync-preferences` switch:

    $ chromium --disable-sync-preferences

If Chromium is started in the background when you login in to your desktop environment, make sure the command your desktop environment uses is:

    $ chromium --disable-sync-preferences --no-startup-window

### Search engines

Make sites like wiki.archlinux.org and wikipedia.org easily searchable by first executing a search on those pages, then going to Settings > Search and click the Manage search engines.. button. From there, "Edit" the Wikipedia entry and change its keyword to w (or some other shortcut you prefer). Now searching Wikipedia for "Arch Linux" from the address bar is done simply by entering "w arch linux".

Note: Google search is used automatically when typing something into the URL bar. A hard-coded keyword trigger is also available using the ? prefix.

### Tmpfs

#### Cache in tmpfs

Note: Chromium actually keeps its cache directory separate from its browser profile directory.

To limit Chromium from writing its cache to a physical disk, one can define an alternative location via the `--disk-cache-dir=/foo/bar` flag:

    $ chromium --disk-cache-dir=/tmp/cache

Cache should be considered temporary and will not be saved after a reboot or hard lock. Alternatively, use:

    /etc/fstab

    tmpfs	/home/username/.cache	tmpfs	noatime,nodev,nosuid,size=400M	0	0

Warning: Adjust the size as needed and be careful. If the size is too large and you are using a sync daemon such as psd on a conventional HDD, it will likely result in very slow start-up times of your graphical system due to long sync back times of the daemon.

#### Profile in tmpfs

Relocate the browser profile to a tmpfs filesystem, including `/tmp`, or `/dev/shm` for improvements in application response as the entire profile is now stored in RAM.

Use an active profile management script for maximal reliability and ease of use.

profile-sync-daemonAUR is such a script and is directly available from the AUR. It symlinks and syncs the browser profile directories to RAM. Refer to the Profile-sync-daemon wiki article for additional information on it.

### Launch a new browser instance

When you launch the browser, it first checks if another instance using the same profile is already running. If there is one, the new window is associated with the old instance. To prevent this, you can specifically ask the browser to run with a different profile.

    $ chromium --user-data-dir=<PATH TO A PROFILE>

Note: It will not work if you specify a link or even a symlink to your regular Chromium profile (typically `~/.config/chromium/Default`). If you want to use the same profile as your current one for this new instance, first copy the folder `~/.config/chromium/Default` to a directory of your choice, keeping the same `Default` name, and launch the browser using the following command by specifying the parent folder of the `Default` folder you have just copied.

For example, if you copied the Default folder to `~/Downloads`:

    $ chromium --user-data-dir=~/Downloads

### Directly open *.torrent files and magnet links with a torrent client

By default, Chromium downloads `*.torrent` files directly and you need to click the notification from the bottom-left corner of the screen in order for the file to be opened with your default torrent client. This can be avoided with the following method:

- Download a `*.torrent` file.
- Right-click the notification displayed at the bottom-left corner of the screen.
- Check the "Always Open Files of This Type" checkbox.

For torrent magnet links to open with Deluge automatically when they are clicked, run the following commands:

Note: If you would like to use, e.g. Transmission instead of Deluge, you can use `transmission-gtk.desktop` here instead.

    $ gvfs-mime --set x-scheme-handler/magnet deluge.desktop
    $ xdg-mime default deluge.desktop x-scheme-handler/magnet

### Touch Scrolling on touchscreen devices

Chrome and Chromium do not support touchscreen by default. There are a couple settings you can change in the "Flags" portion of Chrome to potentially make it work for your device. This has been tested in chromium from the official repositories and google-chromeAUR from the AUR.

- Browse to chrome://flags and set everything to default
- Switch "Enable Touch events" to "Enabled" (chrome://flags/#touch-events)
- Restart Chrome and touch scrolling should work. If it does not, it is worth trying the other modes that are available.

Known bugs:

- Touch Scrolling sometimes stops working after resuming from suspend. Restarting the browser seems to fix it.
- Touching tabs to switch to them is unstable. There is no known fix for this yet.
- You may need to specify which touch device to use. Find your touchscreen device with `xinput list` then launch Chromium with the `--touch-devices=x` parameter, where "x" is the id of your device.

### Disable system tray icon

Open the URL `chrome://flags` in the browser. Disable this flag:

- `device-discovery-notifications`

Click the restart button at the bottom of the page.

## Profile maintenance

Chromium uses Sqlite databases to manage history and the like. Sqlite databases become fragmented over time and empty spaces appear all around. But, since there are no managing processes checking and optimizing the database, these factors eventually result in a performance hit. A good way to improve startup and some other bookmarks- and history-related tasks is to defragment and trim unused space from these databases.

profile-cleanerAUR and browser-vacuumAUR in the AUR do just this.

## Security

### Disable insecure RC4 cipher

The RC4 cipher has been declared as insecure, but the cipher is still in Chromium at present. To disable it:

    $ chromium --cipher-suite-blacklist=0x0001,0x0002,0x0004,0x0005,0x0017,0x0018,0xc002,0xc007,0xc00c,0xc011,0xc016,0xff80,0xff81,0xff82,0xff83

You can check which cipher suites are supported by your browser at https://cc.dcsec.uni-hannover.de/. Make sure to visit this page before and after you make the change to verify that the change was effective.

To make the change persistent, you can modify `~/.config/chromium-flags.conf` and add the flags above. To check, open the website mentioned before. An alternative is to grep inside of your process list for the keyword "cipher".

External Information

There is no cleaner way to disable RC4. Also, the source-code only shows the right hexadecimal value for the single cipher. See Wikipedia:RC4 for basic information and a recommendation to disable RC4.

German Blog showing how to disable RC4 in common browsers.

### User Agent

By default, Chromium already sends an excessively detailed User Agent, as is viewable via the EFF's Panopticlick test. This alone makes each browser readily identifiable with high accuracy, and is further exacerbated by the use of non-stable versions (for example, versions not recently provided by Google's release channels, or versions customized by a distribution).

However, this User Agent can be arbitrarily modified at the start of Chromium's base instance via its `--user-agent="[string]"` parameter.

For the same User Agent as the stable Chrome release for Linux i686 (at the time of writing, the most popular Linux edition of Chrome) one would use:

    --user-agent="Mozilla/5.0 (X11; Linux i686) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/20.0.1132.47 Safari/536.11"

An official, automatically updated listing of Chromium releases which also shows the included WebKit version is available as the OmahaProxy Viewer.

### SSL certificates

Chromium does not have an SSL certificate manager. It relies on the NSS Shared DB `~/.pki.nssdb`. In order to add SSL certificates to the database, users will have to use the shell.

#### Adding CAcert certificates for self-signed certificates

Grab the CAcerts and create an `nssdb`, if one does not already exist. To do this, first install the nss package, then complete these steps:

    $ mkdir -p $HOME/.pki/nssdb
    $ cd $HOME/.pki/nssdb
    $ certutil -N -d sql:.

    $ curl -k -o "cacert-root.crt" "http://www.cacert.org/certs/root.crt"
    $ curl -k -o "cacert-class3.crt" "http://www.cacert.org/certs/class3.crt"
    $ certutil -d sql:$HOME/.pki/nssdb -A -t TC -n "CAcert.org" -i cacert-root.crt
    $ certutil -d sql:$HOME/.pki/nssdb -A -t TC -n "CAcert.org Class 3" -i cacert-class3.crt

Note: Users will need to create a password for the database, if it does not exist.

Now users may manually import a self-signed certificate.

#### Example 1: Using a shell script to isolate the certificate from TomatoUSB

Below is a simple script that will extract and add a certificate to the user's `nssdb`:

    #!/bin/sh
    #
    # usage:  import-cert.sh remote.host.name [port]
    #
    REMHOST=$1
    REMPORT=${2:-443}
    exec 6>&1
    exec > $REMHOST
    echo | openssl s_client -connect ${REMHOST}:${REMPORT} 2>&1 |sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'
    certutil -d sql:$HOME/.pki/nssdb -A -t TC -n "$REMHOST" -i $REMHOST
    exec 1>&6 6>&-

Syntax is advertised in the commented lines.

Reference:

- http://blog.avirtualhome.com/adding-ssl-certificates-to-google-chrome-linux-ubuntu

#### Example 2: Using Firefox to isolate the certificate from TomatoUSB

The firefox browser can be used to save the certificate to a file for manual import into the database.

Using firefox:

1. Browse to the target URL.
2. Upon seeing the "This Connection is Untrusted" warning screen, click: I understand the Risks > Add Exception...
3. Click: View > Details > Export and save the certificate to a temporary location (`/tmp/easy.pem` in this example).

Now import the certificate for use in Chromium:

    $ certutil -d sql:$HOME/.pki/nssdb -A -t TC -n "easy" -i /tmp/easy.pem

Note: Adjust the name to match that of the certificate. In the example above, "easy" is the name of the certificate.

Reference:

- http://sahissam.blogspot.com/2012/06/new-ssl-certificates-for-tomatousb-and.html

## Making flags persistent

Note: Starting with `chromium 42.0.2311.90-1` only per-user flags are supported.

You can put your flags in a `chromium-flags.conf` file under `$HOME/.config/` (or under `$XDG_CONFIG_HOME` if you have configured that environment variable).

No special syntax is used; flags are defined as if they were written in a terminal.

- The arguments are split on whitespace and shell quoting rules apply, but no further parsing is performed.
- In case of improper quoting anywhere in the file, a fatal error is raised.
- Flags can be placed in separate lines for readability, but this is not required.
- Lines starting with a hash symbol (#) are skipped.

Below is an example `chromium-flags.conf` file that defines the flags `--start-maximized --incognito`:

    # This line will be ignored.
    --start-maximized
    --incognito

Tip: If you have Pepper Flash installed, the launcher will automatically pass the correct flags to Chromium so you do not need to define any `--ppapi-flash-*` flags.
Warning: The `chromium-flags.conf` file is specific to Arch Linux and is supported via a custom launcher script that was added in `chromium 42.0.2311.90-1`.

## See also

- Profile-sync-daemon - Systemd service that saves Chromium profile in tmpfs and syncs to disk
- Tmpfs - Tmpfs Filesystem in `/etc/fstab`
- Official tmpfs kernel Documentation

Category:

- Web browser