Find out what caused that stutter

By the time Task Manager is open, it is over

"The mouse stutters sometimes." "It locks up for a second." Two things make this class of symptom hard, and neither of them is about having the right tool — they are about what time you started looking.

• When

  The evidence is already gone

  A symptom that clears in a few seconds has left no trace by the time Task Manager finishes opening. All that remains is your memory of it, so the only move left is to sit and wait for it to happen again.

• What

  Averages do not show it

  For the few seconds it is frozen, disk latency and queue depth spike — while CPU, memory and GPU all read perfectly normal. Watching averages, or a "current value" readout, shows nothing happening at all. Smooth those seconds into a one-minute average and they are gone.

So StallScope is not "a light, tidy monitoring tool". It is built for one thing: to already be running before the symptom, and to still have the evidence afterwards.

Features

Every design decision here is derived from those two problems.

• Measures the freeze itself

  Every performance counter is a candidate cause and nothing more. StallScope times how late its own monitoring thread wakes up, and that is the only number that answers "did the machine actually stop?" Anything past 200ms is written to the stall log by default.

• Never collapsed into a single figure

  Each core and each drive gets its own columns, all of them kept. "Save only the largest one" makes the distribution impossible to reconstruct later, and a single pinned core is invisible in the _Total column.

• A window you can open mid-symptom

  The last hour is drawn from an in-memory ring buffer, so opening the window reads nothing from disk. Starting to load days of logs while the machine is frozen would defeat the purpose.

• The tray icon is the measurement

  One bar is 12 seconds; five bars are the last minute. Bar height is the worst reading in that interval, and a bar that crossed the threshold turns red. You can choose what the bars carry, and by default the icon picks whichever measure is most strained. Whatever you choose, wake-up delay keeps a band of its own across the top, so the icon never stops answering "did it actually freeze".

• Episodes, ranked causes, per-process involvement

  The report pulls out the abnormal intervals, ranks candidate causes by deviation normalised against their own quiet-time spread, and shows what was running at the time. You can lower the thresholds and re-run it.

• Runs with ordinary user rights

  No elevation is ever requested. The self-test measures the collection cost on the spot; on the development machine it came to 9.0ms per second, or 0.90% of one core.

Same symptom, different causes

Freezing is the result, not the cause. StallScope keeps every indicator from the moment it froze, side by side, so one symptom can be separated into distinct causes.

• It froze, but disk and CPU were both fine

  If committed memory alone was pinned at its limit, the machine was waiting on an allocation. Task Manager’s default "Memory" column shows the working set, which still looks comfortable — you cannot get here without recording commit separately.

• Disk latency and queue spike at the moment it froze

  With CPU and memory both reading normal, that is an I/O stall on the storage. The averages stay calm throughout, so it is invisible afterwards unless it was kept per drive at one-second resolution.

• Overall CPU is low, yet it stutters

  If a single core was pinned, the problem is the thread running on it. Total utilisation and the _Total column never show this.

• Short interruptions, over and over

  A rise in DPC or interrupt time points at driver work. It is recorded per core, so which core it happened on is still there afterwards.

What settles it is never one indicator on its own — it is that the others were normal. That is why nothing is collapsed into a summary and everything is kept side by side.

Screens

Every image below is the real rendering code’s own output, not a mockup.

Pricing

Both tiers record exactly the same thing. Pro adds ways of reading it.

Markers and daily summaries are recorded on the free tier too. The day you activate Pro, everything up to that point is already there to read.

• The app itself is free from the Microsoft Store. What you buy here is the Pro key — buying it does not install anything.
• Once payment goes through, your licence key appears on the confirmation page and arrives by email. Enter it in the settings window to turn Pro on.
• Cancel any time from the settings window. Pro stays on until the end of the period you have paid for, and the free features stay after that.

One key covers up to three machines at once. A machine you have not used for 30 days drops off on its own.

Payment is handled by Stripe. Card details never pass through the app.

Price, payment and cancellation terms (statutory notice)

Requirements

OS

Windows 10 version 1809 or later, or Windows 11 (64-bit)

Where it writes

One drive other than the system drive. If C: is what freezes, the recording must not freeze with it — this is the default.

Disk use

About 10MB per day compressed. Kept for 14 days by default.

Interface language

English and Japanese. Follows the Windows display language by default, and can be switched in the settings window.

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