I make Shiny, so weigh this comparison accordingly. I've tried to write it the way I'd want it written if I were the buyer: honest about where Memory Diag wins, where Shiny does, and clear about the setup that many people end up with.
At a glance
| Shiny | Memory Diag | |
|---|---|---|
| Price | $4.99 once, forever | Free + ~$4-5 Pro upgrade |
| Macs covered | Up to 3 personal Macs | Typically 1 Mac |
| Focus | Action (cleanup) | Visibility (monitoring) |
| Pressure graph | No | Yes - live, colour-coded, beautiful |
| Cleanup depth | Deep: orphaned helpers, idle apps, inactive memory | Light: mostly a purge wrapper |
| Telemetry | None | Some |
| Made by | THEODOREHQ | Rocky Sand Studio (small indie) |
Where Memory Diag wins
I want to open here, because comparison posts that gloss over the other side's genuine strengths are not useful.
The pressure graph is genuinely excellent. Memory Diag's signature feature is a live, colour-coded memory pressure graph that sits in your menu bar. Green means your Mac is comfortable. Yellow means it is starting to compress memory. Red means things are tight. At a glance, without opening anything, you can see exactly what state your Mac is in. Shiny does not have this. If you want that visibility, Memory Diag is the one that provides it, and it does so beautifully.
It's free to start. The core monitoring feature, the graph itself, is free. The Pro tier (around $4-5) adds icon customisation and additional menu-bar layout options, but the thing most people want costs nothing to try. If you are not sure whether you care about memory monitoring, starting with Memory Diag free is the sensible first step.
Actively maintained, well-designed. Rocky Sand Studio is a small indie operation, but the app is looked after. The design is polished and the update history is solid. This is not an abandoned utility from 2017; it is a cared-for product.
The Pro tier is modest in price. At around $4-5, the Pro upgrade is genuinely affordable. If you want icon customisation and layout flexibility in your menu bar, the ask is small.
Where Shiny wins
Cleanup depth. Memory Diag's clean button is largely a wrapper around macOS's built-in purge command. That flushes inactive memory and is not nothing; you will see your free RAM number jump. But it does not close orphaned helper processes that have detached from their parent apps, it does not pause idle applications that are quietly consuming memory in the background, and it does not target the accumulated background junk that builds up over a long session. Shiny does all of these. The single click does more.
Three Macs for one price. Shiny's $4.99 license covers up to three personal Macs. If you have a MacBook plus a desktop, or you and a partner share Macs in the same household, one purchase covers everyone. Memory Diag is typically per device.
Zero telemetry. Shiny collects no analytics, no crash reports, no usage data, nothing. Memory Diag collects some. If data collection matters to you, Shiny is the stricter option.
One tier, no decisions. Shiny has a single flat price. There is no free version to outgrow, no upgrade prompt, no Pro gate. You buy it, it works, that is the entire relationship. Memory Diag's free-to-Pro path is a legitimate model, but it introduces a moment where you have to decide whether to pay. With Shiny, that moment is the only one.
Action-oriented interface. Shiny's UI is deliberately minimal: a memory reading, a button, a result. No graphs, no stat panels, no settings to configure. Some people find that limiting; others find it freeing. If you want to act rather than analyse, the single button is the point.
Can you use both together?
Yes, and this is genuinely the setup I'd recommend for people who want both visibility and action.
Memory Diag's graph lives in your menu bar and gives you a constant read on memory pressure. When the graph tips yellow or red, that is your signal. You open Shiny, click once, and the cleanup runs: helper processes closed, idle apps paused, inactive memory released. The graph goes back to green.
If you want the graph AND the action, run them both. The action half is what Shiny does, in one click.
The two apps do not conflict. They solve different parts of the problem and the menu-bar footprint of running both is minimal.
Bottom line
If you want a beautiful live pressure graph to understand your Mac's memory at a glance: Memory Diag. Its graph is its strength, and the free tier delivers it at no cost. The cleanup action is a secondary feature for this app, not its core job.
If you want active cleanup rather than monitoring, and you want it to go deeper than a purge wrapper: Shiny. $4.99 once, three Macs, no telemetry, no upsells, and cleanup that closes the processes Memory Diag leaves alone.
If you want both: run both. Memory Diag for the graph, Shiny for the action. It is a sensible setup and the two apps are designed for different jobs, so there is no meaningful overlap or conflict.
For a wider view of the category, the best Mac memory cleaner for 2026 roundup compares five options side by side. And if you are weighing a similar free-versus-paid trade-off, the Shiny vs Memory Cleaner comparison covers similar ground with a different competitor. If you're asking the broader question of whether any of these tools are worth using at all, are Mac cleaners worth it gives an honest answer.