How it works
A signature is made with a private key that belongs to a certificate, issued after a check of the publisher's identity. When the app is downloaded, Windows or macOS verifies it: a valid signature shows the publisher's name, while an unsigned or altered file triggers a warning or is blocked. Phones go further, as Android and iOS refuse to install unsigned apps at all.
On Windows this is Authenticode, with certificates from a certificate authority (CA) such as DigiCert or Sectigo, or from Microsoft's Azure Artifact Signing service (formerly Trusted Signing). Since 2023 private keys must live on hardware, a USB token or a cloud HSM (hardware security module), and since 2024 pricier EV certificates no longer skip SmartScreen's warnings: reputation builds as a signed app is downloaded. MSIX apps in the Microsoft Store are signed by Microsoft for free.
On macOS, apps distributed outside the Mac App Store are signed with a Developer ID certificate, which needs the Apple Developer Program, then sent to Apple for notarisation, an automated malware check. Gatekeeper blocks apps that skip these steps, and recent macOS versions make opening them deliberately awkward. Linux has no central scheme; package repositories sign their packages instead.
Code signing pros and cons
Pros
- Users see a named publisher instead of an 'unknown publisher' warning
- Proves the file was not tampered with between build and download
- Expected by app stores, auto-updaters and many company networks
Cons
- Costs money every year, plus identity checks that can take days
- Keys kept on hardware tokens are awkward to use from CI build servers
- On Windows a new app can still meet SmartScreen warnings until it builds reputation
When to use Code signing
Pick it when
- Any app you distribute to the public on Windows or macOS
- Software for businesses, whose IT policies often block unsigned programs
Skip it when
- Internal tools on machines where IT installs a trusted certificate itself
- The app ships only as MSIX through the Microsoft Store, which signs it for you
Code signing pricing
Paid
Windows: Artifact Signing about $10 a month (only in some countries) or an OV certificate about $150 to $300 a year. macOS: included in the Apple Developer Program, $99 a year (about ₹9,000).
Code signing pricing page (opens in a new tab)Approximate, checked September 2026.What the other tools cost
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