Short answer: real blue light glasses come with a measured blocking percentage and the wavelength range it applies to, and what you see matches the claim. A lens that blocks most blue light will look clearly yellow, orange or red. A clear lens can be genuine too, but it will filter much less. Two checks take under a minute at home: the tint test and the blue screen test.
Below: seven ways to check a pair, from quick home tests to a professional measurement, plus the red flags to watch for.
Why It's Worth Checking
Blue light glasses are easy to make and easy to label. A 2020 study in Clinical and Experimental Optometry found that blue-blocking lenses on sale varied widely in how much they actually filtered, even between products sold for the same purpose. Checking protects you from:
- Paying for glasses that filter far less than the label suggests
- Choosing the wrong lens for when you use screens, for example a light clear lens for late-night use
7 Ways to Tell If Blue Light Glasses Are Real
1. Look for Measured Data
Genuine brands publish what their lenses block, and how they know. Look for three things:
- A blocking percentage, for example 35% or 99%
- The wavelength range it applies to, for example 400–500nm
- Who tested it, and against which standard
"Blocks harmful blue light" with no numbers tells you nothing. We publish all three for every lens on our science page, measured by Micro-Light Optics against ISO 12312-1 and ANSI Z80.3.
2. Check the Numbers Add Up
The claim and the look of the lens should agree. Filtering blue light takes blue out of what you see, so the more a lens blocks, the warmer it looks:
- Clear lenses typically filter a modest share. Ours blocks 35% across 400–500nm.
- Yellow lenses filter more. Ours blocks 60%.
- Orange and red lenses filter almost all of it. Ours block 99% and 99.7%.
A lens that looks completely clear but claims to block 90% or more of blue light doesn't add up.
3. The Tint Test
Hold the glasses over a sheet of white paper, or look at a white screen through them. A blue light lens will make white look slightly cream, yellow, amber or red, depending on how strong it is. Take them off and compare. If there's no difference at all and the glasses claim strong blocking, be suspicious. See our lens color guide for what each tint looks like.
4. The Reflection Check
Hold the glasses under a bright lamp and tilt them. Many clear blue light lenses show a blue or purple sheen: that's a reflective coating bouncing part of the blue light away. A faint green tinge usually means an anti-reflective coating instead.
This check only applies to clear lenses. Tinted lenses usually filter by absorbing light, so they don't need to show a blue reflection to be genuine. More in why blue light glasses reflect.
5. The Blue Screen Test
Search for a plain, solid blue image (pure RGB blue) and open it full screen on your phone or computer. Look at it with and without the glasses:
- Through an orange or red lens, bright blue should look very dark, close to black.
- Through a yellow lens, it should look noticeably darker and duller.
- Through a clear lens, it should look a little dimmer, but only slightly.
It takes under a minute, and it's the quickest way to see whether a tinted lens is really filtering.
6. The Blue Flashlight Test
Blue light test kits pair a small blue flashlight with a test card. Shine the flashlight at the card, then hold the lens in between: the stronger the filter, the more the blue spot fades or disappears. Some kits use a violet laser pointer instead. Never look into it or shine it toward anyone's eyes.
7. Ask an Optometrist to Measure Them
Many optometrists have a spectrophotometer or lens meter that measures how much light a lens lets through at each wavelength. It's the only way to get a precise figure yourself, so it's worth asking if you're unsure about a pair.
Red Flags
- No blocking percentage, or a percentage with no wavelength range
- Very high blocking claimed for a lens that looks completely clear
- Only UV protection mentioned. UV400 matters, but it isn't the same as filtering blue light
- Vague claims such as "complete protection" or "blocks harmful blue light"
- No information about who tested the lenses
- A price that seems too good for the claims made. Cheap glasses can be fine, but very cheap ones rarely come with measured data
Frequently Asked Questions
How Do I Know If My Glasses Filter Blue Light?
Try the tint test and the blue screen test. If white looks warmer and solid blue looks darker through the lenses, they're filtering blue light. How much depends on the lens.
Can Clear Blue Light Glasses Be Real?
Yes. Clear lenses can genuinely filter blue light, just less than tinted ones. Ours blocks 35% across 400–500nm. Be wary of clear lenses that claim very high figures.
Does a Purple Reflection Mean They're Real?
On a clear lens it usually means there's a reflective blue light coating. It doesn't tell you how much it filters. Tinted lenses often don't show one at all and can still filter strongly.
