“Can I… in the new Edge?” (Un-FAQ)

This post is intended to collect a random set of questions I’ve been asked multiple times about the new Chromium-based Edge. I’ll add to it over time. I wouldn’t call this a FAQ because these questions, while repeated, are not frequently asked.

Last Update: May 14, 2021

Can I get a list of all of the command line arguments?

Unfortunately, we are not today publishing the list of command line arguments, although in principle we could use the same tool Chromium does to parse our source and generate a listing.

In general, our command-line arguments are the same as Chromium‘s, with the exception of marketing names (e.g. Chrome uses --incognito while msedge.exe uses --inprivate) and restricted words (sometimes Edge replaces blacklist with denylist and whitelist with allowlist). Note: The peter.sh list linked here is automatically generated; check the Last automated update occurred on text to verify that it was updated recently.

Can I block my employees from accessing the edge://flags page?

You can add “edge://flags” to the URLBlocklist if desired. Generally, we don’t recommend using this policy to block edge://* pages as doing so could have unexpected consequences.

Note that, even if you block access to edge://flags, a user is still able to modify the JSON data storage file backing that page: %LocalAppData%\Microsoft\Edge\User Data\Local State using Notepad or any other text editor.

Similarly, a user might specify command line arguments when launching msedge.exe to change a wide variety of settings.

Can I disable certain ciphers, like 3DES?

The new Edge does not use SChannel, so none of the prior SChannel cipher configuration policies or settings have any effect on the new Edge.

Group Policy may be used to configure the new Edge’s SSLVersionMin (which does impact available cipher suites, but doesn’t disable all of the ciphers considered “Weak” by SSLLabs.com’s test). Microsoft Edge 85+ offers a TLSCipherSuiteDenyList Group Policy. In contrast, Chrome explicitly made a design/philosophical choice (see this and this) not to support disabling individual cipher suites via policy.

Ciphersuites in Edge may also be disabled using a command-line flag:

msedge.exe --cipher-suite-denylist=0x000a https://ssllabs.com

A few other notes:

  • The cipher suite in use is selected by the server from the list offered by the client. So if an organization is worried about ciphers used within their organization, they can simply direct their servers to only negotiate cipher suites acceptable to them.
  • The Chrome team has begun experimenting with disabling some weaker/older ciphersuites; see https://crbug.com/658905
  • If an Enterprise has configured IE Mode, the IE Mode tab’s HTTPS implementation is still controlled by Internet Explorer / Windows / SChannel policy, not the new Edge Chromium policies.
  • If TLS/1.3 is enabled, you cannot use the cipher-suite-denylist to disable ciphers 0x1301, 0x1302, and 0x1303. TLS1.3 spec: “A TLS-compliant application MUST implement the TLS_AES_128_GCM_SHA256 [GCM] cipher suite and SHOULD implement the TLS_AES_256_GCM_SHA384 [GCM] and TLS_CHACHA20_POLY1305_SHA256 [RFC8439] cipher suites (see Appendix B.4).”

Can I use TLS/1.3?

TLS/1.3 is supported natively within the new Chromium-based Edge on all platforms.

Chromium-based Edge does not rely upon OS support for TLS. Windows’ IE 11 and Legacy Edge do not yet support TLS/1.3, but are expected to support TLS/1.3 in a future Windows 10 release.

For the time being, enabling both TLS/1.3 and TLS/1.2 is a best practice for servers.

Can I turn off TLS/1.3?

You can set the SSLVersionMax command line argument, but the associated Group Policy was removed in Chrome 75.

msedge.exe --ssl-version-max=tls1.2 https://ssllabs.com

Can Extensions be installed automatically?

Enterprises can make extension install automatically and prevent disabling them using the ExtensionInstallForcelist Policy. Admins can also install extensions (but allow users to disable them) using the ExtensionSettings policy with the installation_mode set to normal_installed.

Here are the details to install extensions directly via the Windows Registry. Please note that if you want to install extensions from the Chrome WebStore, then you must provide the Chrome store id and update url: https://clients2.google.com/service/update2/crx.

Can specific file types be set to auto-open? Can I change my mind?

After downloading a file, you can click the “…” menu next to the download item and choose “Always open files of this type” from the context menu:

This option is not available for all file types (e.g. file types deemed dangerous cannot be auto-opened).

One challenge with this UI is that after you set this option, the download bar will not be shown for this file type any longer, leaving you no way to untick the “Always open files of this type” menu item.

The secret to changing your mind is to visit edge://settings/downloads and click the Clear all button next to the File types which are opened automatically after downloading list. There is no way to clear just one file type from the list short of editing the profile’s PREFERENCES json directly.

Presently, no Group Policy is available to force file types (except PDF) to open automatically, but this is a common enterprise request. The Master Preferences file can be configured with this option, but those defaults are only used when creating new browser profiles, and users may change them.

Can I go directly to single-word (Intranet) sites without doing a search first?

Can I avoid doing a search with a notification bar saying “Did you mean to go to <http://payroll&gt;?” In Internet Explorer, there was a “Go to an intranet site for a single word entry in the Address bar” checkbox in the Advanced Settings.

Use the GoToIntranetSiteForSingleWordEntryInAddressBar policy to change the default behavior.

Can I use URLs of unlimited size?

Within Chromium, URLs of up to 2mb can be used in general, although some UI surfaces will truncate URLs at 32kb. For performance and other reasons, I would not recommend using URLs over that smaller size.

Can I use configure Edge to use more than 6 HTTP/1.1 connections per host?

No. Using parallel connections as was common in HTTP/1.1 suffers from lower performance and increased load on the server. As a hacky workaround to exceed the 6 connections-per-host limit, some sites use “sharding” which assigns multiple DNS names to a single server. Because browser connection limits are based on the hostname, this allows the client to make 6*NumShards parallel connections.

Chromium exposes only a policy to control the maximum connections per proxy server, but there is no policy to control the maximum connections per web server. This sometimes leads to problems in niche scenarios, but we have not, as yet, heard a non-trivial number of complaints.

In the ideal case, the site would deploy HTTP/2 or HTTP/3, which multiplex many (Chromium default 100, server configurable to up to 256) requests over a single TCP/IP connection, eliminating head-of-line blocking and providing much better performance vs. legacy HTTP/1.1.

Can I use Group Policy to turn off HSTS for specific sites?

No. There is no policy that turns of HSTS for a host that had requested it.

The HSTSPolicyBypassList policy description leads users to believe it does something it does not. I filed a bug to get the text clarified.

The policy should read something like:

Setting the policy specifies a list of hostnames that bypass preloaded HSTS upgrades from http to https. Only single-label hostnames are allowed in this policy, and the policy only applies to HSTS-preloaded “static” entries (“app”, “new”, “search”, “play”, etc”). This policy does not prevent HSTS upgrades for servers that have explicitly requested HSTS upgrades using the Strict-Transport-Security response headers. Supplied hostnames must be canonicalized: Any IDNs must be converted to their A-label format, and all ASCII letters must be lowercase. This policy only applies to the specific single-label hostnames specified, not to subdomains of those names.

Some users complain that they’re getting HSTS for “localhost” sites and try to use this policy to prevent that. Localhost is not on the HSTS Preload list. If your browser is HSTS-upgrading localhost, it’s because it received a Strict-Transport-Security response header from Localhost that turned on HSTS. To fix that:

  1. Stop sending the header
  2. On edge://net-internals/#hsts, use the Delete domain security policies section to remove Localhost
  3. Or you can hit Ctrl+Shift+Delete to open the Clear Browsing Data dialog and choose Cached Images and Files. This will delete ALL dynamic HSTS rules.

Can I control Permissions (like Allow Popups) based on the Site’s IP address?

The Permissions system’s “Site Lists” feature does not support specifying an IP-range for allow and block lists.

It does support specification of individual IP literals, but such rules are only respected if the user navigates to the site using said literal (e.g. http://127.0.0.1/). If a hostname is used (http://localhost), the IP Literal rule will not be respected.

How does visiting a site in Internet Explorer open Edge automagically?

Edge installs a Browser Helper Object into Internet Explorer with a pre-provisioned site list.

Other than that, a site can try to launch a link using the microsoft-edge:// URL protocol.

Can I turn off cross-origin security in Edge?

You shouldn’t.

The flag –disable-web-security command line flag is not supported (that is to say, we won’t guarantee what it does or does not allow, and it could disappear at any time), and hasn’t been updated to account for all of the various security features added to the browser over the last few years (see https://crbug.com/1150447). Launching the browser with this flag makes that browser instance inherently unsafe to use. That was also true of the old “Access data sources” flag in IE, although the IE-flag was at least Zone-limited.

The command must be paired with a user-data-dir argument:

msedge.exe –disable-web-security –user-data-dir=C:\temp example.com

Developers should fix the dependent target sites to emit proper Access-Control-Allow-Origin headers so that the web’s same-origin-policy is respected.

If they do not control the target site, they will need to build a server proxy (browser->their-server->remote-server) that sets the correct ACAO headers.

Published by ericlaw

Impatient optimist. Dad. Author/speaker. Created Fiddler & SlickRun. PM @ MSFT '01-'12, and '18-, presently working on Microsoft Edge. My words are my own.

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