Use the Firefox private browser.

I'd like too

Approximately half of browser users don't even know what privacy is and what the browser does. Most of them probably up-voted this suggestion, LOL

https://www.theregister.co.uk/2018/04/24/private_web_browsing_study/

Iron Browser from srware.com is Google's Chrome with the Google tracking and GUID stuff removed.

I would rather they work together with brave and have brave add their VPN service.

But why... You already have lots of web browsers, just do some research.
https://en.wikipedia.org/wiki/List_of_web_browsers
Also, it's almost impossible to build both new rendering and javascript engines from sratch with all the features already available on Blink and V8. Even tho they were both developed by Google, they're fully open-source and extremely efficient, that's why Opera, Vivaldi and even Brave decided to use those engines.
That being said, why would you build a browser using these engines, as there are already lots of browsers... Plus, you'd need mobile versions in order to sync the favorites on all your devices.
Me, personally, I like to stay as google-less as possible, and for that same reason I use Firefox (with SpiderMonkey and Gecko engines).
Btw there are firefox versions (since firefox is fully-open-source) focused on user privacy (WaterFox).

I took my vote back as I believe ProtonMail should focus on making a secure email service for everyone as it has a lot to improve. Personally its more important that its designed in a way that users don't get stuck in its ecosystem.

There is no need for another privacy friendly browser, because there are already some... I think PM should for now primarily focus on email related features.
I think using different providers for completely different services is a good thing, because it removes the single point of failure.

I would gladly pay extra for this feature.
Paying $30 per month, is a steal for all the services you provide me with.

Just use Tor or DuckDuckGo browser, or Firefox with adding...

@ Christopher Dalton Very simply Chris your question is "48 shades of grey" what exactly do you want?? one hand you want google/chrome interface but you dont like there tracking ( that is how they are designed to track every click and page) BUT If you want security use TOR (the onion ring) Go the whole hog and set up a VPN and a half decent firewall on an old 486 box or lappy.. itzUp2U You can have your cake and eat it too, if you graze on both sides of the fence robbo

there are a lot of safe browsing projects,
IMHO protonmail should focus all energy to provide the best email service.

People who upvoted this topic dont realize that its not a solution:

While browsers could be improved to resist fingerprinting, there is no point in creating a new one. If you want to improve privacy on the web, effort should be applied to secure data transfer standards or decentralized file systems (e.g. Tor, i2p, GNUnet, Matrix, Zeronet, IPFS, et cetera.)

http://secushare.org

The greatest security & privacy risk on the internet today is NOT the browser — its the lack of a global standard protocol for secure mail transfer which encrypts all metadata and supports forward secrecy. Any available resources should be directed at solving this problem first. If you want to improve browsing security, just use Firefox with Ublock, Umatrix (for power users), Ghostery, Canvas Defender, cookie autodelete, and VPN.

TOR ..hmmm
https://surveillancevalley.com/blog/fact-checking-the-tor-projects-government-ties

Get passport,id card,driving license,visas,permit etc.[globalimmigrationathomy@gmail.com]

Downvote. Waste of protonmails time. Use Firefox with ublock or noscript.

Just use Firefox with ublock origin this would be a waste of time and there's more things to focus on.

Secure Browser would be great!!! Protecting against all threats and vulnerabilities such as Java flaws and WebRTC leaking true IP address behind protection such as vpn.

Browser
1) https:// force all pages to use (minimal) or advise you that page doest have ssl etc
2) to work in conjunction with proton vpn if required
3) Browser sand box for testing purposes of dogy links that may be launching malicious code to steal peoples details and money etc
4) virus protection built in and firewall? nice to have
5) recommendation app that will check and validate the link based on other sources (nice to have)

Its seems these days so shocking that we have to go to these lengths of protecting our data from data theft and other entities when this is our world and our global network. But thanks to the good guys such as proton and others lets hope that they will never get brought out with the promise of money by super power.

Thats just basic list that maybe will help everybody in some way.

Where

Don't be fooled, no where is really "safe", except that outside the US it is safer than in the US.