MediumAbout 8 minutesBoth

Every website says Not secure or the connection is not private

All sites give me a certificate warning. Is my computer infected?

CF

Written by The CommonFixes team · fact checked by CommonFixes review desk

Last updated

Short answer

Almost always a wrong system clock, but it can also be antivirus HTTPS scanning or, rarely, adware that installed its own root certificate. The quickest thing to try first: fix the clock first — Settings, Time and language, and press Sync now. A date even a day off invalidates every certificate on the internet. Most people are done in about 8 minutes.

Full walkthrough below: 4 steps for Windows and Mac, rated medium.

Sounds like this

  • NET::ERR_CERT_DATE_INVALID
  • Your connection is not private on every site
  • Only happens on this one computer

Why it happens

Almost always a wrong system clock, but it can also be antivirus HTTPS scanning or, rarely, adware that installed its own root certificate.

Work through these in order

0% done
  1. 1

    Fix the clock first

    Settings, Time and language, and press Sync now. A date even a day off invalidates every certificate on the internet.

  2. 2

    Test in a private window

    Open an incognito window. If sites load fine there, a browser extension is intercepting traffic. Disable extensions one by one.

  3. 3

    Turn off HTTPS scanning temporarily

    In Avast, AVG, Kaspersky or ESET, find the HTTPS or SSL scanning setting and switch it off. Reload the site to confirm.

  4. 4

    Clear the SSL state

    Search Internet Options, Content tab, Clear SSL state, then restart the browser.

If none of that worked

Check installed programs for anything you did not install and run a Malwarebytes scan. Adware that installs a root certificate causes this on every browser at once.

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Who wrote this and how we checked it

CF

The CommonFixes team

Writer and researcher

We are a small group of people who spend our days repairing laptops and desktops for family, friends and small offices. Every guide here starts with a problem someone actually brought to us, and we only write down the steps that put the machine right.

  • Everyday repairs
  • Windows and Mac
  • Plain language
RD

CommonFixes review desk

Technical editor

Before a guide goes live, a second person walks through it on a real machine and checks each instruction against the maker's own support pages. Anything we cannot confirm is removed rather than guessed at.

  • Fact checking
  • Safety warnings
  • Source links

This guide was last updated on 10 August 2026. If a step no longer matches what you see on screen, tell us on the contact page and we will test it again.

A gentle reminder: back up anything you cannot afford to lose before major repairs. If a step ever feels risky, stop and ask a technician. There is no shame in that.