$Why I built RetinaDesk

I bought a 27 inch 4K monitor for my MacBook Pro and stared at fuzzy text for two weeks before I realized the monitor was not broken. macOS was.

Well, not broken. Just designed for one specific pixel density that almost no monitor on Amazon actually hits. Apple drew the entire system around 218 PPI. A 27 inch 4K panel runs at 163 PPI. The math does not work, and your eyes feel it before your brain catches up.

I went looking for a guide. What I found was Windows centric review sites talking about HDR brightness and 240Hz panels. None of it helped me pick a monitor that would look right on a Mac. So I built RetinaDesk.

The problem nobody else was solving

Every monitor review site treats macOS as an afterthought. They benchmark on Windows test rigs. They compare gaming features. They never explain why a "4K monitor" can look beautiful on a PC and soft on a MacBook Pro sitting next to it.

The answer is HiDPI scaling. macOS does not do fractional scaling well. It targets a 2x pixel doubled mode, which means it expects roughly 218 PPI on the panel. Hit that target and macOS renders crisply with no interpolation. Miss it, and the system has to scale, smear, and resample everything you see.

Only two monitor categories hit 218 PPI exactly. 5K at 27 inches. 6K at 32 inches. That is the whole reason this site exists. No 4K, no ultrawide, no gaming panels. Just the displays that give a Mac the density it was built for.

The three tools

Reviews are the boring part of any monitor site. The fun part for me was building tools. I wanted utilities that answered the questions I asked myself before buying my own display. Each one solves a different problem in the order you actually hit them.

1. Mac External Display Support tool

Apple Silicon chips are not equal. The base M1, M2, M3, and M4 officially drive one external monitor. The Pro, Max, and Ultra raise that limit and add HDMI 2.1. The per port resolution caps differ. The valid configurations differ.

This tool lets you pick your exact Mac, from M1 to M5, and see the max external display count, per port resolution and refresh caps, and the configurations that are actually supported. All sourced from Apple. You check this first, before you even start shortlisting monitors, so you do not waste time falling in love with a 6K panel your base M3 cannot drive.

2. Mac PPI Calculator and Retina Checker

This is the tool I wish existed before I bought that 4K. You enter a resolution and screen size. It converts that into pixel density and shows how macOS HiDPI scaling will render text on the panel. There is a live pixel grid and a 218 PPI reference for comparison.

It is the bridge between a spec sheet and reality. A 32 inch 4K sounds great until the calculator tells you it is 137 PPI. A 27 inch 5K sounds expensive until you see it land exactly on 218.

3. Mac Cable Bandwidth Calculator

This is the silent killer of Mac monitor setups. Most "my monitor only runs at 30Hz" problems are not the monitor. They are the cable. A 5K 60Hz signal needs around 22 Gbps. 6K 60Hz needs roughly 36 Gbps before compression. 4K 120Hz needs about 32 Gbps.

The calculator takes a resolution, refresh rate, and bit depth, computes the required bandwidth, and compares it against HDMI 2.0 and 2.1, DisplayPort 1.4, USB-C DP Alt Mode, and Thunderbolt 3, 4, and 5. It tells you if the cable you already own can carry the signal you want. Most of the time, it cannot, and that is why people end up with banded color or 30Hz desktops.

The tech stack

RetinaDesk is fully static. No backend, no database, no edge functions. Just HTML, CSS, and a sprinkle of client side JavaScript for the calculators.

• Astro as the framework. Static site generation is the right model for a content site that updates a few times a month. Astro ships almost zero JavaScript by default, which keeps Lighthouse scores green and load times under half a second on a cold cache.
• Cloudflare Workers for hosting. Pages would have worked, but I went with the Workers static assets setup for tighter control over caching headers and routing. Global edge delivery, free SSL, zero cold start.
• Vanilla JS for the tools. No React, no Vue, no Svelte. The three calculators are small enough that hand written DOM updates are faster to write and faster to ship than any framework would be. The PPI calculator is under 200 lines.
• Tailwind for styling, scoped per Astro component. The dark theme is a single CSS variable file. The serif headings are Instrument Serif, the body is Inter.
• No analytics tracking by default. No cookies, no consent banner needed. Cloudflare gives me enough aggregate traffic data without sending anything to a third party. The whole site is under 2MB transferred for a typical visit, including images. The HTML for a monitor review is around 30KB. The tools each ship under 10KB of JavaScript.

What I learned

Niching down works. A site that only covers two monitor categories has less to write about, which means I can write each piece in real depth. The ranking is short enough to actually mean something.

Static is enough. I keep wanting to add a backend for "personalization" or "saved comparisons" and every time I stop myself. The site does not need it. The tools run in the browser. The reviews are flat HTML. Cloudflare serves the whole thing for free and faster than any database backed setup ever would.

Tools rank well. The PPI calculator and the cable bandwidth calculator pull in search traffic that buying guides cannot reach. People searching for "is my cable fast enough for 6K" do not want a 4000 word review. They want one answer. Giving them that answer earns trust, and the trust is what brings them back when they are actually ready to buy.

If you have a Mac and you have been wondering why your monitor looks slightly wrong, the answer is probably 163 PPI. Come visit. The tools are free.