// GET NESSIE
Get Nessie
Nessie is a Windows installer, deliberately not code-signed, so check the file's SHA-256 before you run it. The free five-hour trial is not available yet.
Free five-hour trial
Nessie on your own PC for five hours, free. Some automatic features stay off in the trial so its restore at the end can always finish.
The free trial is not available yet. There is no trial download today. When the trial installer (nessie-trial-setup.exe) has been built and checked, it will appear here with its own SHA-256.
Nessie
The full app, paid once, for one PC: Sentinel, Competitive mode and its session reports, measured Optimize, Restore everything, learning (beta) and bug-fix updates.
The key you were given or bought. Checking it here does not use up its one PC.
Nessie is deliberately not code-signed. Instead, the SHA-256 of each file is published here. In PowerShell, run:
Get-FileHash "$env:USERPROFILE\Downloads\nessie-setup.exe"Build of September 26, 2026 · version 1.3.4 · 26.6 MB. The Hash it prints must match exactly:
1D08F03F98F1FF4F0FE40C81AD5068A00DA2C13C7248D5FFA2A09E1A57AFFAF9If it does not match, do not run the file; email [email protected]. You can also look up this exact file on VirusTotal or upload your copy there yourself: same hash, same report.
Install
- Buy Nessie on this site: $35, paid once. Your license key is shown after payment and emailed to you.
- Enter your key in this card to unlock the download, then download nessie-setup.exe and check it before you run it (below).
- Run it and approve the Windows prompts; the guide further down shows each one. The installer puts Nessie in Program Files.
- Open Nessie and paste your key. It activates on one PC; to move it to another PC, email [email protected]. Nessie then asks which of four things it may do on its own, and all four start off.
- When a newer version is published, Nessie tells you. Update now downloads it, checks it, installs it over your copy and reopens Nessie; nothing is downloaded until you press it.
- To remove it, uninstall Nessie from Windows Settings, Apps. The uninstaller runs Restore everything Nessie changed first, unless you choose to keep your current settings, and shows the result.
Pressed No on the Windows administrator prompt? Nothing was installed; run the file again and choose Yes. What Windows shows
Already have a key
Check that your key is active, then paste it into Nessie when it asks. A key activates on one PC.
Lost your key? Email [email protected] from the address you bought with.
Invited to the private beta? Get the current private-beta installer. Your test key is supplied separately.
// WHAT WINDOWS SHOWS
Four warnings you may see, and what to do.
Nessie is deliberately not code-signed, so Windows cannot name its publisher and warns you. That is expected. What protects you is the SHA-256 check above: if the hash matches, the file is the one I built.
step 1 / 4
The browser's download warning
Right after the download finishes, in Microsoft Edge's downloads panel.
“nessie-setup.exe isn't commonly downloaded. Make sure you trust nessie-setup.exe before you open it.”
- Point at the download and choose the three dots (More actions), then Keep.
- Edge asks again: choose Show more, then Keep anyway.
- Chrome and Firefox can show a similar notice; choose Keep.
New files from small developers get this until enough people have downloaded them. Check the SHA-256 before you open the file.
Microsoft Edge downloads panel saying nessie-setup.exe isn't commonly downloaded, with the Keep option step 2 / 4
“Windows protected your PC”
When you open the installer, in a blue Microsoft Defender SmartScreen window.
“Microsoft Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk.”
- Choose More info. Windows shows the file name and Publisher: Unknown publisher.
- Check that the file name is nessie-setup.exe or nessie-trial-setup.exe, then choose Run anyway.
“Unknown publisher” is expected: Nessie is deliberately not code-signed. The SHA-256 on this page is how you know the file is the one I built.
The blue Windows protected your PC window after choosing More info, showing Unknown publisher and the Run anyway button step 3 / 4
Smart App Control
Only on Windows 11 PCs where Smart App Control is on, which is usually only after a fresh Windows install.
Windows says Smart App Control blocked an app that may be unsafe, and offers no Run anyway button.
- If you see this for the trial, stop there: the paid app will meet the same block, so do not buy it.
- Email [email protected] and say which Windows version you have. It helps me find out how often this happens.
I will not ask you to lower your PC's protection for Nessie. Result of my own test on a clean Windows 11 PC with Smart App Control on: still to be added here.
The Windows 11 Smart App Control message blocking an unsigned installer step 4 / 4
The administrator prompt (UAC)
When the installer starts, and each time you open Nessie yourself, because changing system settings needs administrator rights.
“Do you want to allow this app from an unknown publisher to make changes to your device?” with Verified publisher: Unknown.
- Check the program name is the Nessie file you downloaded, then choose Yes.
- If you chose No, nothing was installed or changed. Run the file again and choose Yes.
The User Account Control prompt for nessie-setup.exe showing Verified publisher: Unknown