How do you watch a solar eclipse safely?
The short answer
Use eclipse glasses certified to the ISO 12312-2 standard, or skip glasses entirely and project the Sun's image onto paper through a pinhole. Sunglasses never work, no matter how many pairs you stack. The only moment it is safe to look unaided is during true totality, when the Sun is completely covered.
Why the rule is absolute
The lens at the front of your eye focuses light to a sharp point on the retina, in the same way a magnifying glass focuses sunlight onto paper. Pointed at the Sun, it does exactly what you would expect. The dangerous part is that the retina has no pain receptors at all. Damage happens with no sensation whatsoever, and you discover it hours later, when it may already be permanent. There is no warning signal to rely on, which is why the rule allows no exceptions.
Eclipse glasses are not strong sunglasses
Proper eclipse glasses are thousands of times darker than sunglasses. Through them the entire world goes black except one thing: a calm, dim disc of Sun. Check three things on every pair. Look for the ISO 12312-2 stamp, which is the international safety standard. Check the filter for scratches or pinholes against a bright lamp. Buy from a reputable seller rather than an unknown bargain listing. If a pair fails any one of those checks, do not use it.
Three habits that prevent accidents
First, glasses go on before you look up, never after. Second, they come off only while you are looking down at the ground, not while facing the sky. Third, and this one catches people out: never look through binoculars, a telescope or a camera while wearing eclipse glasses. Those lenses gather so much light that they will burn straight through the filter in an instant. Filters for optical equipment must be fitted over the front of the instrument, never between the instrument and your eye.
Projection needs no filters and is completely safe
Take a cereal box, cover one end with foil, make a tiny pinhole in it, and tape a strip of white paper inside the other end. Add a small viewing hole in the side. Stand with your back to the Sun, let light fall through the pinhole, and look at the paper. A small image of the Sun appears, and when the eclipse begins, the bite appears on your paper screen. You watch the screen, never the sky.
Pinhole projectors are everywhere once you know
A kitchen colander is fifty pinholes at once; hold it up and the ground fills with fifty small crescent Suns. A straw hat works. A cracker works. The best one is free: stand under a leafy tree and every gap between the leaves acts as a pinhole, scattering crescent-shaped light across the ground. Most people walk straight past this during every partial eclipse without ever noticing it.
Ninety-nine percent is not totality
This is the single most common and most dangerous mistake. If the Sun is 99 percent covered where you are standing, the remaining sliver is still blinding daylight and glasses stay on the entire time. Only inside the narrow path of totality, and only during the brief window when the disc is completely covered, is it safe to look unaided. The instant the first spark of Sun reappears, protection goes straight back on.
Sources
Full transcript: 5 Safe Ways to Watch the 2026 Eclipse
sunglasses will not save your eyes Not one pair not 10 pairs stacked together Watch straight through On August the 12th the sun gets a bite taken out of it Everyone's going to want to look up And today you'll learn how to do it the right way Grab a grown-up This one's for them too Welcome back to "Watt & Why" 15 days to the eclipse Today how to watch it without hurting your eyes Share this one First why the rule exists The front of your eye is a lens A really good one Its whole job is taking light and focusing it down to a sharp little point at the back of your eye Sunlight same treatment All that blazing light squeezed onto one tiny spot like a magnifying glass focused on paper You know what happens to the paper And here's the sneaky part The back of your eye has no pain sensors None It wouldn't hurt while it happened You'd find out later and it can be forever No pain no warning That's why the rule is absolute So what does work Real eclipse glasses They're not dark like sunglasses They're thousands of times darker Through them the whole world goes black except one thing a calm dim little sun The only safe direct view But they have to be real Flip them over and look for the stamp ISO 12312-2 That's the international safety mark Three checks every single pair The stamp no scratches or pin holes and bought from a real seller not a mystery bargain If a pair fails any check it's out Glasses sorted Drill time Rule one glasses on before you look up not after Before Rule two they come off only while you're looking away Down at your shoes then off Rule three and this one surprises people Never point binoculars a telescope or a camera at the sun with your glasses on Those lenses gather so much light they'll burn straight through the filter One more time Grown-ups too On before up off Looking away Never through anything Now for my favorite part Because you can watch the eclipse with no glasses at all You build a projector Step one a cereal box Step two foil over one end Poke a pin hole in it Tiny Step three a strip of white paper inside the other end Step four a little peekhole in the side Done Now stand with your back to the sun The sun stays behind you always and let its light fall through the pinhole Look through the peak hole and there it is a little glowing sun projected on paper And when the eclipse takes its bite the bite shows up on your paper screen You watch the screen not the sky That's the whole magic And once you know the trick you'll find projectors everywhere Raid the kitchen A colander is 50 pin holes at once Hold it over the ground and get 50 tiny eclipses A straw hat works A cracker works And the best one is free Stand under a tree Every little gap between the leaves is a pinhole and the ground fills with crescent confetti People walk past it every eclipse and never notice Not you Not anymore Now the exception You heard about it in episode 1 If you are standing inside that narrow path on August the 12th there come about 2 minutes when the sun is completely totally covered Totality The sky goes night and only then glasses off It's safe and it's the sight of a lifetime But the instant that first spark of sun comes back glasses straight back on before it after it and everywhere outside the path protected always Because here's the thing most people get wrong Say you're not quite in the path Say the sun gets 99% covered where you live Madrid and Barcelona that's you 99% sounds like totality It is not That last 1% of sun is still blazing daylight still dangerous and your glasses stay on the whole time 99 is not 100 When in doubt glasses on And Thursday I'll show you exactly what each version looks like minute by minute So remember real eclipse glasses Check for the stamp every pair Or skip glasses entirely and project it Serial box colander tree and watch the screen not the sky And glasses come off only inside totality only in the path That's it That's the whole rule book T minus 15 days and now you're the Eclipse safety expert in your house Thursday what you'll actually see minute by minute It's stranger than you think See you on "Watt & Why"
Transcript of the episode, lightly cleaned for readability.
Sample question
Question 1 of 10
Why is looking at the Sun without protection so dangerous?
- The eye focuses sunlight onto the retina, which has no pain receptors to warn you correct
- It causes immediate severe pain
- It makes your eyes water uncontrollably
- It is only dangerous for children
Damage can occur with no sensation at all, and may only be noticed hours later.
That is one of 10. The rest are not shown here, and the answer order changes every time you take the quiz.
Written by Watt & Why. Published 25 July 2026. Last reviewed 17 October 2026.