hckrnws

You can take TWO screenshots, moments apart, open in GIMP, paste one over the other and choose any one of these laying modes:

Lighten, Screen, Addition, Darken, Multiply, Linear burn, Hard Mix, Difference, Exclusion, Subtract, Grain Extract, Grain Merge, or Luminance.

https://ibb.co/DDQBJDKR

> You can take TWO screenshots, moments apart, open in GIMP, paste one over the other and choose any one of these laying modes:

You actually don't need any image editing skill. Here is a browser-only solution:

1. Take two screenshots.

2. Open these screenshots in two separate tabs on your browser.

3. Switch between tabs very, very quickly (use CTRL-Tab)

Source: tested on Firefox

reminds me of this: https://www.reddit.com/r/LifeProTips/comments/5jdzsx/lpt_use...

Is it possible to modify the webpage to make the pattern of the text go down and the pattern of the background do up?

Out of sheer curiosity, I put three screenshots of the noise into Claude Opus 4.1, Gemini 2.5 Pro, and GPT 5, all with thinking enabled with the prompt “what does the screen say?”.

Opus 4.1 flagged the message due to prompt injection risk, Gemini made a bad guess, and GPT 5 got it by using the code interpreter.

I thought it was amusing. Claude’s (non) response got me thinking - first, it was very on brand, second, that the content filter was right - pasting images of seemingly random noise into a sensitive environment is a terrible idea.

Neat idea.

A friend of mine made a similar animated GIF type captcha a few years ago but based on multiple scrolling horizontal bars that would each reveal their portion of the underlying image including letters, and made a (friendly) bet that it should be pretty hard to solve.

Grabbing the entire set of frames and greyscaling them, doing an average over all of them and then applying a few minor fixups like thresholding and contrast adjustment worked easily enough as the letters were reveleaed in more frames than not (I don't think that would affect the difficulty much though if it were any diffierent). After that the rest of the image was pretty amenable to character recognition.

But then that would be a video, not a screenshot

Computer vision mode: and each screenshot together.

Yeah if this became popular, we'd have another Show HN for a tool that automated that.

Or just copy the text from the url. Not very secure, really. :D

Or just ... record a video of the screen.

This game disappears if you pause it: https://youtube.com/watch?v=Bg3RAI8uyVw

This is great - seems to be the same effect of hiding a shape using an animated noise pattern on a background of static noise.

They even provide the source code for the effect:

https://github.com/brantagames/noise-shader

Yes - I was thinking of this. It solves various complicated problems such as rendering distance information in this format.

This is great. The sphere example looks especially pleasing. It also reminds me of the game The Voidness.

First time seeing this, makes me smile involuntarily.

If anybody implements that to antiscrenshot some sensitive data, somebody else will use another phone, a tablet or a camera to record a video of it. Nice idea though.

Or the same one.

While a screencap image hides the message, a screencap video shows it perfectly well.

I first saw this effect in a video from Branta Games.

https://www.youtube.com/watch?v=Bg3RAI8uyVw

The effect is disrupted by introducing rendering artifacts, by watching the video in 144p or in this case by zooming out.

I'd love to know the name of this effect, so I can read more about the fMRI studies that make use of it.

What I've found so far:

Random Dot Kinematogram

Perceptual Organization from Motion (video of Flounder camouflage)

https://www.youtube.com/watch?v=2VO10eDIyiE

https://gist.github.com/jncornett/d7cb397ce3ceff268a0ee1b86f...

On iPhone: screenrecord. Take screenshots every couple seconds. Overlay images with 50% transparency (I use Procreate Pocket for this part)

On Android: Take a look at the URL, see the text in plain-text :)

This should have an epilepsy warning. Or something of that kind. It certainly made me feel sick.

This is more a curious question for those affected by epilepsy. If you know you are triggered by such things how long an exposure is required to trigger an effect. Are you able notice that media may be triggering and simply close it or is exposure and triggering almost instantaneous?

I saw the game using this rendering weeks ago, looked okay. Now I saw a font and tried to hold on to the edges while reading it, and yes, somehow this made me more (sea) sick. Strange.

Perhaps faces would be strongest in terms of reaction.

Oh yes please add a warning. My brain is burning right now!

Others have mentioned Branta Games, but I first saw the effect here: https://youtu.be/TdTMeNXCnTs

This one is actually more sophisticated because it doesn't rely on scrolling pixels like the OP. So the object doesn't just disappear in screenshots, but also when the animation stops moving! So you can't actually display text that stands still, like the "hello" in the OP.

thanks, that's also the best explained one!

a good benchmark for video understanding in IA

Fun!

I always wanted to make text that couldn't be recorded with a video recorder, but that doesn't seem possible.

Maybe if you knew the exact framerate that the camera was recording at, you could do the same trick, but I don't think cameras are that consistent.

I have to admit it's a pretty cool idea.

At first I was worried that there was a (stupid) API in web browsers just like on mobiles to prevent users from screenshotting something by blanking the screen in the screenshot.

This makes me feel motion-sick, which is kind of impressive because I'm normally not easily susceptible to that.

My eyes went straight into seeing 3D image mode. It's the easiest one I've seen yet! /s

Hello fellow person from the 90s. mine eyes did the same too.

Heh my eyes felt like they started bleeding

"The text disappears..." And my eyesight with it

Neat! I've seen stuff like this that works as a magic eye thing. So you cross your eyes (or make them parallel, depending on the type of image) and it makes a 3d animation appear in front of the page.

I’d like to see an example!

As soon as I read the title I knew it would be akin to "Bad Apple that disappears when you pause it"

https://www.youtube.com/watch?v=bVLwYa46Cf0

And another version of this, using apples instead of white noise

https://www.youtube.com/watch?v=r40AvHs3uJE

I don't see any text: just a scrolling down screen of random black/white pixels.

It seems to depend on reading pixels from a canvas. This is commonly used for fingerprinting users on the web, so you have to disable some privacy plugins.

Has anyone tried a long exposure to see if the motion smears into something discernible? Obviously harder to expose a bright screen without some ND since the shutter speed is the phone's main exposure control

Here's the screen recording version of a long exposure (thanks for the nerd snipe) - https://gist.github.com/spro/7599415b0e47de65311557b3454771a...

Perhaps this technique could be defeated by scrolling the background in the opposite direction as the text

If you zoom out to 25 % the text is clearly visible and screenshottable.

Probably the lower frequencies of noise are not matched? Not sure if the frequencies of the order of movement frequency can actually be matched

How do you take a “long exposure” screenshot? Isn’t every screenshot a perfect digital copy of a single frame or a full on video?

Clearly, I meant using a camera, and I'm guessing you knew that too

Not the parent but that was not at all clear to me. I immediately thought of taking multiple successive instantaneous screenshots and then stacking them. I'm not sure I would have thought of using a camera within a few minutes to an hour, it's not a tool I would ever reach for normally.

Oh, so your screenshot utility has "long exposure" and an "ND" filter and "shutter speed" controls, just like a phone's camera? What kind of screenshot utility simulates optical camera effects? What purpose does that serve? Care to share a link to it?

>Obviously harder to expose a bright screen without some ND since the shutter speed is the phone's main exposure control

https://en.wikipedia.org/wiki/Neutral-density_filter

https://en.wikipedia.org/wiki/Shutter_speed

I just did this with 50% transparency. It works

Also not the parent but how the hell did you not understand what "long exposure" means ffs

Because the context is about screenshots and context matters

"ffs".

I uploaded two images to ChatGPT and asked it to XOR them and give me the result in text.

Appreciate that it handles emoji as well. Can't distinguish between smileys though.

I also appreciate that Hn removes emojis from comments. :'(

Doesn't even show anything on LibreWolf, probably disabled WebGL as usual. I thought it was a nice error screen, but apparently it was intended, just without the text :P

Seems to work if you disable canvas fingerprinting protection.

This idea has made me think of another subject - would it be possible to overload a face / car plate scanning camera by using a pattern, like qr code for exampl? Or a jacket made of qr codes?

Reminds me of dazzle camouflage.

https://en.wikipedia.org/wiki/Dazzle_camouflage

Could someone please post what this disappeared bit is supposed to look like? Looks legible to me when I screenshot and open in Preview on MacOS 15.6.1 (Firefox).

You are probably browsing with zoom, that seems to screw up the up rendering and makes the background and text look different. It should be just black&white random pixel noise for both background and foreground, without motion the text becomes invisible, as it blends with the background.

Another idea I had with this concept is to make an LLM-proof captcha. Maybe humans can detect the characters in the 'motion' itself, which could be unique to us?

- The captcha would be generated like this on a headless browser, and recorded as a video, which is then served to the user.

- We can make the background also move in random directions, to prevent just detecting which pixels are changing and drawing an outline.

- I tried also having the text itself move (bounce like the DVD logo). Somehow makes it even more readable.

I definitely know nothing about how LLMs interpret video, or optics, so please let me know if this is dumb.

Take N screenshots, XOR them pairwise, OR the results, then perform normal OCR.

I don't think we need more capable people thinking of silly captchas.

As if captchas aren't painful enough for visually impaired users...

Cool. I used the Windows snipping tool and just screen-recorded it.

It's a nice effect, but I don't think it's usable in practice, because it's not accessible for visually impaired users: not enough contrast between foreground text and background

Not technically a screenshot, I guess, but trivially easy to do with software I had lying around all the same. https://media4.giphy.com/media/v1.Y2lkPTc5MGI3NjExYXloZ3Z0NT...

Firefox on Android seems to just be a static image, I can't see any text.

Probably the result of canvas fingerprinting protection configured in your `about:config`? With a default profile it seems to work fine on Firefox for Android.

I haven't changed any of that on here.

Looks like I consistently get just the static image when I open in a new tab then switch to it, but then if I refresh the page without switching tabs it'll show the animation.

Wfm

Yeah but the randomness may produce all kinds of NSFW stuff ...

Also, it's even harder to read than most captchas.

But fun idea, it was nice to see.

Even is some have found a workaround, this is a cool feature

Sure, but I can just record a video instead. It doesn’t disappear then!

What i am supposed to see here? Its just static noisy background

Had the same in LibreWolf under Manjaro Linux. Worked in Chrome.

Animation, but only inside a border that is the letters of Hello.

This could be used for Captcha systems. Would current bots be able to decipher these?

Ha cool! How’s it work?

The only way to see the text is in the movement. The pattern across any single frame is entirely random noise.

> The pattern across any single frame is entirely random noise.

This is untrue in at least one sense. The patterning within the animated letters cycles. It is generated either by evaluating a periodic function or by reading from a file using a periodic offset.

Can't it be continuous random noise added at the top and then moved down each frame.

Roughly you create another full size rect. On each frame add a random pixel on row 1 and shift everything down.

Make that rest a layer below the top one which has Hello cut out as transparent.

In any single frame the result is random noise.

You could do that, but that's not what the page is doing.

You don't even need to maintain the approach of having the pattern within the text move downwards over time. You could redraw it every frame with random data, as if it was television static. It would still be easy to read, as long as the background stayed fixed.

It's not a great visual, but like this: https://michaelbach.de/ot/cog-Dalmatian/

You can also break it by recording the screen, of course.

same thing, but a game: https://brantagames.itch.io/motus

For what it's worth, there are some websites that embed some crazy shit when you screenshot. On reddit, r/CenturyClub will fill your background with a slightly off-white version of your username so that they can identify leakers, and I'm not certain how exactly they do it.

If you blink really fast, the text almost disappears.

firefox on linux with a bunch of css stuff set to defaults or none !important shows a static image

Fun side effect: staring at the letters for a bit makes the rest of the image move.

but screen recording works :)

In your phone, just record the screen, then drag the player to see how every still pic blend in within the surroundings, but as soon as it moves it shows up.

Had a lot of fun trying to break this. Turns out you can screenshot real easily by zooming out. Maybe there are other ways but I stopped trying :)

yeah - I actually was initially confused since I wasn't having any issues screenshotting it but had forgotten that I have the default site zoom set to ~65%.

Not sure what you mean - I can screenshot it freely that's not the point the point is if you look then at the screenshot you cant discern the text because its a single frame now

He's right. This is zoomed out: https://imgur.com/a/G7CKZ94

This is on MacOS 15.6, Chromium (BrowserOS), captured with the OS' native screenshot utility. Since I was asked about the zoom factor, I now tried simply capturing it at 100% and it was still perfectly readable...

I guess the trick doesn't work on this browser.

I zoomed out to 90% and could make out something was there but wasn't easy to read. Zooming out further went back to just being noise. I also tried zooming in but with no success. What zoom level did you use and I guess we have to ask the standard what browser/version/OS/etc?? My FFv142 on macOS never took a screen grab like you did

This is really interesting - because it means the "randomness" is different between the text and the background, and when you zoom out enough, the eye can distinguish it?

hmmm I think it's probably just an aliasing / canvas drawing issue. When I bring a screenshot in heavily zoomed out 33% - the pixels comprising the "HELLO" shape have a significantly higher luminance than the rest of the background.

Zooming out before taking screenshot and the text is no longer obfuscated. I tried and confirmed it works. In fact, the text is perhaps even more readable than the original.

It depends how fast or slow your GPU is. I tried it and saw the effect you described, but within a second or two it started moving and was obscured again. Obviously you could automate the problem away.

Mine freezes the animation on zoom change. Not sure you could automate against that

What I meant was that even if it only freezes for a second, you could automate the screenshots to be captured during that time instead of trying to beat the clock manually

Screnshotted fine in Xfce.

The text reappears when I screenshot it twice.

Seems trivial to diff multiple screenshots to identify what parts move. Or just use a compression algorithm to do the same.

Would 2 screenshots be enough, I wonder?

Yeah, the letters are big enough, an xor shows the text quite clearly.

"you cannot screenshot this already illegible mess of white noise"

Coinbase was hacked for $400M when literally someone from outsourced support services was taking screenshots on their phone!

The culprit had more than 10k photos of all security details for thousands of wealthy customers.

If it's even true someone from outsourced support has access to some sensitive security details then using this dumpster is almost like throwing your money out of the window.