Edge79+ vs. Edge18 (Edge Legacy) vs. Chrome vs. Internet Explorer

Note: I expect to update this post over time. Last update: July 25, 2022.

Compatibility Deltas

As our new Edge Insider builds roll out to the public, we’re starting to triage reports of compatibility issues where Edge79+ (the new Chromium-based Edge, aka Anaheim) behaves differently than the old Edge (Edge18, aka Spartan, aka Edge Legacy) and/or Google Chrome.

In general, Edge79+ will behave very similarly to Chrome. When comparing Edge and Chrome behavior, be sure to compare against the corresponding Chrome Stable, Beta, Dev and Canary channels; Edge 80 vs Chrome 80, etc.

We expect there will be some behavioral deltas between Edge79+ and its Chrome-peer versions, so I’ll note those here too.

Note: I’ve previously blogged about interop issues between Edge18 and Chrome.

  • For security reasons, Edge79 and Chrome block navigation to file:// URLs from non-file URLs, although Edge 95+ has a policy to somewhat relax that.
  • In Edge18 and Internet Explorer, attempting to navigate to an App Protocol with no handler installed shows a prompt to visit the Microsoft Store to find a handler. In Chrome/Edge79, the navigation attempt is silently ignored.
  • Edge 18 and Internet Explorer offer a msLaunchUri API for launching and detecting App Protocols. This API is not available in Edge 79 or Chrome.
  • Edge 18 and Internet Explorer allow an App Protocol handler to opt-out of warning the user on open using the WarnOnOpen registry key. Edge 79 and Chrome do not support this registry key.


  • Edge shows a Password Reveal icon on password fields; Chrome does not do so on Desktop. If your website shows its own reveal icon, you should use CSS to hide Edge’s.
  • When rendering text/plain files, Chromium wraps the lines of text to the width of the browser window, while Internet Explorer did not. If you need to turn off word-wrapping, you can add a Favorite named NoWrap with the url value:

    javascript:document.body.firstChild.style =

    Clicking the Favorite will disable word-wrapping on the loaded text file.


  • Edge/Chrome have better support for image formats vs. Internet Explorer; e.g. Chromium supports WebP and Animated PNGs. Currently, Edge does not support AVIF while Chrome does.
  • Edge/Chrome have comparatively poor support for the MHTML format.


  • Unlike IE/Edge18, Edge79/Chrome do not support DirectInvoke, a scheme whereby a download is converted into the launch of an application with a URL argument. DirectInvoke is most commonly used when launching Office documents and when running ClickOnce applications. For now, users can workaround the lack of ClickOnce support by installing an extension. Update: In Edge 87+, DirectInvoke is enabled; to enable ClickOnce, see the edge://flags/#edge-click-once setting.
  • Edge79/Chrome do not support the proprietary msSaveBlob or msSaveOrOpenBlob APIs supported in Edge18. In most cases, you should instead use an A element with a download attribute.
  • Edge18 did not support navigation to or downloading from data URLs via the download attribute; Edge79/Chrome allow the download of data URLs up to 2mb in length. In most cases, you should prefer blob urls.

Network Proxy

  • Edge 79+/Chrome adopt the system’s proxy settings by default. If a proxy script is supplied, it is evaluated using the built-in V8 script engine. In contrast, Edge 18 and earlier use the WinHTTP Proxy Service in Windows. Further discussion of the implications of this difference can be found at the end of this post.

    Microsoft DirectAccess and similar networking software may not work properly when Chromium performs proxy determination internally. You can instruct Edge 79+ to use the WinHTTP Proxy Service by launching the browser with the –winhttp-proxy-resolver command line argument. This feature will be exposed to Group Policy in a future release of Edge.
  • Edge 79+/Chrome do not allow loading a PAC script from a file:// URI. (IE allowed this long ago, but it hasn’t been supported in a long time).
  • If you are behind an authenticating proxy server and choose to save your proxy username/password in Edge 18 or Internet Explorer, the WinHTTP Proxy Service will store those credentials in CredMan and reuse those proxy credentials for subsequent challenges even if you restart the browser. The credentials will also be available for silent use by other applications (e.g. the Windows Store app). Even if you don’t tick the “Remember my credentials” checkbox, the proxy credentials will be remembered for the Windows logon session.

    In contrast, if you choose to save your proxy username/password in Edge79+, Chrome, or Firefox, you will be shown an authentication prompt once every time you restart your browser. The username:password will be pre-filled but you must hit “OK” to submit the credentials. Stored credentials will not be available for use by other applications that wish to use the proxy.
  • The myIpAddress() function allows a proxy to determine (one) IP address for the client. However, this function is inherently broken for multi-homed hosts (which have multiple IPs). To decide which IP address to return, Chromium asks the system for a route to an IP address on the Internet.

    Chrome probes the route to / 2001:4860:4860::8888 while Edge 79+ probes the route to / fd3e:4f5a:5b81::1. The probe doesn’t actually send any packets to the target, but if your network is configured to route these addresses differently, your PAC file’s myIpAddress() call could return different results between Chrome and Edge.

Network Protocols & Cache

  • Chrome/Edge79+ support the HTTP3/QUIC protocol. Edge 18 and earlier do not.
  • Generally, Chrome/Edge79+ have enhanced support for caching directives, fixing many limitations in the IE/Edge18 cache. However, one delta is that Chrome/Edge79+ do not respect Cache-Control directives specified by META HTTP-EQUIV directives inside a HTML page. Caching directives must instead be specified in the appropriate HTTP Response headers.
  • Chrome/Edge have removed support for the FTP protocol.
  • Edge Legacy supports the Cache-Control token immutable; Chromium-based browsers do not (yet).
  • Chrome/Edge/Safari will fail responses served over HTTP2 with ERR_HTTP2_PROTOCOL_ERROR if a response header name contains a space. Edge Legacy/Firefox will just ignore the header, and IE will allow it.
  • Chrome/Edge limit granularity of the HTTP Referer header (and the DOM document.referrer property) by default.
  • Internet Explorer historically had a URL Length limit of 2083 (INTERNET_MAX_URL_LENGTH) characters. Over the years, this was relaxed in many places, but not everywhere. Chromium limits URLs to 2mb (kMaxURLChars) for most scenarios, although the URL bar limits the displayed URL to 32kb, and some components that interact with Windows (e.g. marking of downloaded files) will limit URLs passed to those components to INTERNET_MAX_URL_LENGTH for interoperability.

Network Timeouts

Receive timeout

Internet Explorer had a default receive timeout of one hour (a read() call on a socket will timeout after one hour), that could be controlled via the registry. In contrast, I don’t see an attempt to set a timeout in the Chromium code, or a requirement in fetch. Experimenting locally, a top-level navigation does not time out in over an hour. Chromium uses non-blocking reads, so SO_RCVTIMEO is not set, and I don’t see any obvious timeouts in higher levels.

Other timeout trivia

HTTPS – TLS Protocol

  • Edge79 and Chrome enable TLS/1.3 by default; Edge18 does not support TLS/1.3 prior to Windows 10 19H1, and even on that platform it is disabled by default (and known to be buggy).
  • Edge79 and Chrome support a different list of TLS ciphers than Edge18.
  • Edge79 and Chrome send GREASE tokens in HTTPS handshakes; Edge18 does not.
  • Edge79, Chrome, Firefox, and Safari prohibit connections for HTTP/2 traffic from using banned (weak) ciphers, showing ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY if the server attempts to use such ciphers. Edge18 did not enforce this requirement. This has primarily impacted intranet websites served by IIS on Windows Server 2012 where the server was either misconfigured or does not have the latest updates installed. Patching the server and/or adjusting its TLS configuration will resolve the problem. End-users should complain to the server operators, and can work around the problem by closing all instances of Edge then restarting with a commandline argument msedge.exe –disable-http2 to disable support for the faster network protocol.
  • Chrome and Edge use the HSTS Preload list checked into Chromium and generated by HSTSPreload.org. Updates to that list HSTS updates flow through the release channels, so if you get your site added or removed from the HSTS Preload list this week, it’ll be in the Stable release in ~8-12 weeks (0-4 weeks of Canary, 4 weeks of Dev, 4 weeks of beta).

    Perhaps surprisingly, Edge/Chrome do not update the HSTS preload list out-of-band (via the component updater). Internet Explorer (WinINET) updates their version of the list (which is based on Mozilla’s list, which is based on Chromium’s list) very irregularly (~twice a year).

HTTPS – Certificates

  • Edge79 and Chrome require that a site’s certificate contain its domain name in the SubjectAltName (SAN) field. Edge 18 permits the certificate to omit the SAN and if the domain name is in the Subject Common Name (CN) field. (All public CAs use the SAN; certificates that chain to a local/enterprise trusted root may need to be updated).
  • Firefox, Edge79 and Chromium 41+, reject wildcarded SubjectAltNames where the * is not the entirety of the leftmost label. In contrast, Edge18 and IE will match a SubjectAltName of w*.example.com to the server www.example.com while the modern browsers will not.
  • Edge79 and Chrome do not allow server certificate chains that contain SHA-1 signatures. Edge Legacy and IE permit SHA-1 in chains that certificates that chain to a local/enterprise root. A policy added Edge 86 temporarily allowed SHA-1 chains but this policy is no longer available.
  • Edge79 and Chrome require certificates that chain to trusted root CAs to be logged in Certificate Transparency (CT). This generally isn’t a problem because public roots are supposed to log in CT as a part of their baseline requirements. However, certain organizations (including Microsoft and CAs) have hybrid roots which are both publicly trusted and issue privately within the organization. As a result, loading pages may error out with NET::ERR_CERTIFICATE_TRANSPARENCY_REQUIRED. To mitigate this, such organizations must either start logging internal certificates in CT, or set one of three policies under HKLM\SOFTWARE\Policies\Microsoft\Edge. Edge18 does not support CT.
  • For most (non-EV) certificates, Chrome/Edge79 will not request certificate revocation information from the network (OCSP, CRL download), using revocation information only if it’s cached on the client or stapled in the TLS handshake. Internet Explorer and Legacy Edge would actively hit the network for revocation information by default. See What’s the story with certificate revocation? for discussion.
  • Edge79 and Chrome use a custom Win32 client certificate picker UI (Edge’s is slightly enhanced vs. Chrome’s), while Edge18 uses the system’s default certificate picker.


  • Edge79 and Chrome support the Leave Secure Cookies Alone spec, which blocks HTTP pages from setting cookies with the Secure attribute and restricts the ways in which HTTP pages may interfere with cookies sent to HTTPS pages. Legacy Edge does not have these restrictions.
  • Edge79 and Chrome support Cookie prefixes (restrictions on cookies whose names begin with the prefixes __Secure- and __Host-). Legacy Edge does not enforce these restrictions.
  • Edge79, Chrome, and Firefox ignore Set-Cookie headers with values over 4096 characters in length (including cookie-controlling directives like SameSite). In contrast, IE and Edge18 permit cookies with name-value pairs up to 5118 characters in length.
  • Modern Edge and Chrome default to SameSite=Lax for cookies.

Authentication and Login

  • In Edge79, Edge18, and Firefox, running the browser in InPrivate mode disables automatic Integrated Windows Authentication. Chrome (prior to v81) and Internet Explorer do not disable automatic authentication in private mode. You can disable automatic authentication in Chrome by launching it with a command line argument: chrome.exe --auth-server-whitelist="_"

    Starting in Edge 82, flags on the edge://flags page allow re-enabling Automatic Authentication for Guest and InPrivate sessions.
  • Edge18/Edge79 integrates a built-in single-sign-on (SSO) provider, such that configured account credentials are automatically injected into request headers for configured domains; this feature is disabled in InPrivate mode. Chrome does not have this behavior for Microsoft accounts.
  • Edge18 supports Azure Active Directory’s Conditional Access feature. For Chrome, an extension is required. Edge79 has not yet integrated support for this feature.
  • Chrome and Edge 79+ choose the strongest HTTP Authentication scheme advertised by the server, regardless of the order of WWW-Authenticate headers provided. In contrast, Edge 18/IE prioritize the first non-BASIC scheme offered. This can lead the new Edge to choose Negotiate in cases where the older Edge might pick NLTM.
  • By default, Internet Explorer and Edge Legacy would automatically send a client certificate to a server on your Local Intranet if the client only had one certificate available. In Chromium, a Group Policy must be set.
  • Edge Legacy and IE encode BASIC authentication credentials using iso-8859-1. Chromium, Safari, and Firefox use UTF-8 as suggested by RFC7617.


  • Edge18 includes an API window.external.GetHostEnvironmentValue that returns some interesting information about the system, including whether it is running in the “Windows 10 S” lockdown mode. Edge76 and Chrome do not support this API. Update: Edge 78 restored this API with a limited set of tokens:
    {“os-architecture”:”AMD64″,”os-build”:”10.0.18362″,”os-sku”:”4″,”os-mode”:”2″}. The os-mode of 2 indicates a Windows 10 S configuration.
  • Edge18 and Internet Explorer are the only browsers that consider all local-PC file:// URIs to be same-origin, allowing them to refer to other resources on the local computer. Other browsers treat file origins as unique, blocking DOM interactions between frames from different files, blocking transform of XML files using adjacent XSL files, etc.
  • Google Chrome ships with the Portable Native Client plugin; Edge79 does not include this plugin. The plugin is little-used and you’re unlikely to encounter problems with its absence except on the Google Earth website. PNaCl is deprecated in favor of WebAssembly and is slated to be removed from Chrome in Q2 2019.
  • The Edge Platform Status site also includes a short list of features that are supported in Edge18 but not Chromium-derived browsers.
  • The HTML5 SpeechRecognition API fails silently in Edge 76 to 82 because we do not connect to Google Web Services and have not yet done the work to hook this API up to a Microsoft Web Service. Forum thread. Update: This works on Windows as of Edge 100, but appears to be unreliable on Mac. The team is investigating.
  • The Edge Legacy and IE implementation offer only a limited set of WebCrypto algorithms (Test page) and have some undocumented limits (e.g. you must use a 12byte IV for AES-GCM). The Chromium implementation offers better support for a wider variety of scenarios.
  • In Chromium today, the resizable windowFeature (passed in calls to window.open()) is used as a signal about whether the new window should contain the toolbar and be launched as a popup rather than a new tab; it does not prevent resizing of that popup. Notably, neither Firefox nor Safari allows this windowFeature to prevent the user from resizing the resulting browser window; only IE respects the directive.

Group Policy and Command Line Arguments

Edge79+’s Policy List includes a set of Group Policies that match Chrome’s Group Policies and Edge’s command line arguments generally match Chrome’s. The minor changes include:

If you’re using the registry to set a policy for Edge, put it under the


…node instead of under the



If you’re trying to use a Chrome command line argument when launching in the new MSEdge.exe and it’s not working, check whether it has “blacklist” or “whitelist” in the name. If so, we probably renamed it.

For instance, want to tell Edge not to accept a 3DES ciphersuite for TLS? You need to use

msedge.exe --cipher-suite-denylist=0x000a

…instead of

chrome.exe --cipher-suite-blacklist=0x000a

….as you would with Chrome.


Chrome and Edge 79+ make very limited use of the Windows Security Zones architecture. See this post for more information.

In contrast, Internet Explorer made extensive use of Zones to control security and compatibility changes. By way of example, back in IE8, a change was made to the browser such that the file upload control would no longer send the full path of an uploaded file. For instance, when uploading C:\users\ericlaw\desktop\ThisIsMyFile.jpg to the server, the browser would instead send C:\fakepath\ThisIsMyFile.jpg. The main reason is privacy: we didn’t want the remote website to be able to infer that the user uploading the file was named EricLaw based on the information about their local file system paths. This redaction became a web standard—now ALL browsers send fakepath and doing so is required by the HTML specification. However, for compatibility reasons, Internet Explorer would only apply this protection to sites in the Internet Zone; sites loaded in the Intranet zone would continue to send the unredacted file path. This behavior is controlled by the “Include local directory path when uploading files to a server” setting in the Internet Control Panel:

Modern browsers, including Microsoft Edge, do not have any setting like this one; there’s no way to turn off the redaction of the file path. Available workarounds would be to either 1) Put this site in IE Mode, or to 2) restructure the application such that it does not attempt to get a local file path from the user using a File Upload control.


Browsers identify themselves to servers using a User-Agent header. A top source of compatibility problems is caused by sites that attempt to behave differently based on the User-Agent header and make incorrect assumptions about feature support, or fail to update their checks over time. Please, for the love of the web, avoid User-Agent Detection at all costs!

Chrome User-Agent string:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36

Edge77 Beta (Desktop) User-Agent string:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.19 Safari/537.36 Edg/

Edge18 User-Agent string:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 Edge/18.18362

Edge73 Stable (Android) User-Agent string:
Mozilla/5.0 (Linux; Android 10; Pixel 3 XL) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.90 Mobile Safari/537.36 EdgA/

You’ll note that each of the Edge variants uses a different token at the end of the User-Agent string, but the string otherwise matches Chrome versions of the same build. Sites should almost never do anything with the Edge token information– treat Edge like Chrome. Failing to follow this advice almost always leads to bugs.

Sites are so bad about misusing the User-Agent header that Edge was forced to introduce a service-driven override list, which you can find at edge://compat/useragent. Alas, even that feature can cause problems in unusual cases. For testing, you can tell Edge to ignore the list by starting it thusly:

    msedge.exe --disable-domain-action-user-agent-override

Upcoming Changes

Perhaps the biggest change with the move to the new Chromium-backed Microsoft Edge is a much faster pace of change in the Web Platform. You can keep an eye out on upstream changes using the ChromeStatus schedule page, and Microsoft’s list of site-impacting-changes.

Stay compatible out there!


Published by ericlaw

Impatient optimist. Dad. Author/speaker. Created Fiddler & SlickRun. PM @ Microsoft 2001-2012, and 2018-2022, working on Office, IE, and Edge. Now a SWE on Microsoft Defender Web Protection. My words are my own, I do not speak for any other entity.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: