Understanding Browser Channels

Microsoft Edge (and upstream Chrome) is available in four different Channels: Stable, Beta, Dev, and Canary. The vast majority of Edge users run on the Stable Channel, but the three pre-Stable channels can be downloaded easily from microsoftedgeinsider.com. You can keep them around for testing if you like, or join the cool kids and setContinue reading “Understanding Browser Channels”

Certificate Revocation in Microsoft Edge

When you visit a HTTPS site, the server must present a certificate, signed by a trusted third-party (a Certificate Authority, aka CA), vouching for the identity of the bearer. The certificate contains an expiration date, and is considered valid until that date arrives. But what if the CA later realizes that it issued the certificateContinue reading “Certificate Revocation in Microsoft Edge”

Chromium Internals: PAK Files

Web browsers are made up of much more than the native code (mostly compiled C++) that makes up their .exe and .dll files. A significant portion of the browser’s functionality (and bulk) is what we’d call “resources”, which include things like: Images (at two resolutions, regular and “high-DPI”) Localized UI Strings HTML, JavaScript, and CSSContinue reading “Chromium Internals: PAK Files”

Chromium’s DNS Cache

From the mailbag: Q: How long does Chromium cache hostnames? I know a user can clear the hostname cache using the Clear host cache button on about://net-internals/#dns, but how long it will take for the cache to be removed if no manual action is taken? After changing DNS records on my server, nslookup from aContinue reading “Chromium’s DNS Cache”

Smarter Defaults by Paying Attention

As a part of every page load, browsers have to make dozens, hundreds, or even thousands of decisions of varying levels of importance: should a particular API be available? Should a resource load be permitted? Should script be allowed to run? Should video be allowed to start playing automatically? Should cookies or credentials be sentContinue reading “Smarter Defaults by Paying Attention”

MHTML in Chromium

The MHTML file format (aka “Webpage, single file”) allows a single file to contain the multiple resources that are used to load a webpage (script, css, images, etc). Edge (Chromium) has code to provide limited support for MHTML, though it retains an option to use the format when saving the current page via Ctrl+S orContinue reading “MHTML in Chromium”

Download Blocking by File Type

Last Updated: 16 August 2022 I’ve previously gushed about the magic of the File Type Policies component — a mechanism that allows files to be classified by their level of “dangerousness”, such that harmless files (e.g. .txt files) can be downloaded freely, whilst potentially-dangerous files (e.g. .dll files) are subjected to a higher degree ofContinue reading “Download Blocking by File Type”

Per-Site Permissions in Edge

Last year, I wrote about how the new Microsoft Edge browser mostly ignores Security Zones (except in very rare circumstances) to configure security and permissions decisions. Instead, in Chromium per-site permissions are controlled by settings and policies expressed using a simple syntax with limited wildcarding support. Settings Page’s Site Permissions and Group Policy Internet ExplorerContinue reading “Per-Site Permissions in Edge”

window.close() Restrictions

Sometimes, Web Developers are surprised to find that the window.close() API doesn’t always close the browser window. When looking at the Developer Tools console, they’ll see a message like: Scripts may close only the windows that were opened by them. Why Do Browsers Limit close()? Before we dive into what factors govern what happens whenContinue reading “window.close() Restrictions”