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Comments on How does Zalgo Text work, and how can I prevent my application from accepting it?

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How does Zalgo Text work, and how can I prevent my application from accepting it?

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A Zalgo Text is something like this:



T̃͟͏̧̟͓̯̘͓͙͔o̤̫͋ͯͫ̂ ̥͍̫̻͚̦͖͇̌ͪ̇ͤ̑̐͋̾̕i̢͖̩͙͐͑ͬ̄̿̍̚ͅn̵̢̼̙̳̒̄ͥ̋̐v̡̟̗̹̻̜͕̲ͣ̐ͤͤ͒́oͫ͂̆͑ͩ҉͇̰͚̹̠̫͔̗k̷̭̬̭͙̹̺̯ͩ̌̾̒̋̓ͤ͛͘͠e̥͙̓̄̕ ̵̫͈ͪţ̱̺̺̑̿̉̌͛̂̇h͙̣̬̓̂͞ę̡̲̟͎͉̟͛̓̉̆̉͘ ͍̯̱͎̬͍ͬ̒ͣͩ͟͡ḥ̗͖̝̮̗̼ͮ̋̉̃͐̿ͪͅi̞͉̯͖̞͉̙ͬͦ̄͋̈̂ͥ̊́̕v̶̝̼̫͔̬̯̯ͯ͑̈͠e̪͓͕̦̪̗̠ͯ͛͌̀̉͘ͅ-̍̉ͦ̈́͌͏̸͉͍͖̥͓̭̗̖mͣͣͪ̇͂͏̳̤̺͓̜̪͙͕i͋̏̎ͤ͆́͏̛̰͉̮̬͙̩̩ͅn̴̴̞̗ͩ̓̉̋̕d̝͇̬̣́̃ͦ̀͡ ̖̩̞̯̇̍́̆ͮͤ̄ͬ͂͜͡r̷͎͙͉̀͒͐͛́è̫̹͙̔ͭͦ͑ͩͮͯṗ̶̸͍̺̘͈́̄ͫ̅ͣ̇̃̚r̨͚͎̙̻̜ͬͬ̆͆e̩̞̹͈̱͕ͮ̈́̒̑͛̊̌͛͘ŝ̱̹̠̂ͭͦ̅̅͛̚͜e̝̳̞̊̍̐ñ͔̟̳̱͔ͣ̅̄ͮt̴̫̻̮̤̿̆̂̊͘i̷̫ͤͨ̏ͤͧͅͅn̛̜̠͋͐͆̆͑̎̍͑̚g̶̜ͧ́ͭͯ͐ͬ͛̇͜ ̳̩͉̣̤̜̰̠̌ͤ̆̚͟c̷̝̥͉͓͕͓͇̣͉̒̈̇ͧ͆̌ͣͣ͟ḩͥ̅ͥ̇ͩ͗҉̳͎̱ą̍̀͆͑̈́͂҉͍̤̘͔̹̭̱͢o̥̮̘ͨ̎̄̎́͢s̯̮̖͒.̨͋̈́͑̈́ͪ̚҉̻͓͔̤̯̲̤̺̀ ̔ͨ̋̾̒̋̚̚͏͓̰͙̘͈I̧̗͇ͮ͠n̠̬͗ͮ̿ͭ͌̉̈ͦv̦͚͇̠̹̰̭ͤo̭̞ͫ̃ͨ̏ͥ̒́̚k̯̱͛ͫ͆͂̇͡͝i̗̪͎͈͕͚̥̫ͥ͂̐n̖̤͔̟̖͇̠͋̐̀ͅͅg̛͑ͪ͏͇̪͓̘ ̎̒ͯͥͭ͂͏̠͇̮̪t̡͍̫̘̯̼̣̋ͤ̒h̨͇͕̺͍͈̠͖̤̱ͮ̃e͖̝̣̽ͬ͊̀ ͍ͫ̅̆͊́͌͡fͫ̾͏̭͎̰̣̱̺̯̥é̻̪͖͙̮͓̊̌̓ͩ̑̆ē͙̤̪͈͉̦̭͛̃ͩͧͭ̏͒̕͢ľ̡҉̪͙̻̣̪̼̲i̜ͯ̄̐͠͝n̸̨̩̰̺̱̗̍̉̄̉̆͐̎g̹͖͈ͥ͗̍͝ͅ ̙̹͉̰̪̠͍͖͔ͧ̾̈́ͫ̔͋̈̍o̵̤̥͍ͬ̐̀̿̇ͯ̅f̵̜̟͚́͛͜͠ ̺̭̆̑ͭc̶̢̫̭͓̭̐͗h͍͉̞̩͕ͮ̉́͛͑ͤͯ͒͡ä̜̱͙͎̯̟ͮ̂͑̄͊̍̑͜oͫ̋̿͌͢͏̟̲̗s̵̮̟̙̻̗̭̲͂̍͑͑͂ͤ́̚ͅ.̵̨͉̟͓ͦͯͬͤ͌ͧ͑̾ ̝̥̰͋ͬ͂̋͛͑̚W̶̹̹̣̟͕ͪͤ̽̀i̳̪͉͇͇̟̲̇̃́ͧ̾ͭ̿̆ͯ͡t̬̪̬̑̿͊͊́̚h̋͑̈̇͋҉̴͖̜ͅͅo̴̠̭̯̫̽ͨṳ̡̟͕̝̦͓͖̪̇́́͢t̬̙̖̝͈͔̻͛͊ ̵̛̗̝̝̰̫̞̠̙̽̄̊͆o̺̮͆ͯ͊͑ͭ̚̕ṙ̶̟̺̱̜̺̻̘̰̀͊ͮ̀͡ḋ̢̰̂̎ͦͥe̛̩͍̯̍ͭͩͤͦ̚r͍̲̾ͯ̊͛͡.̮̙͙̠̦̜̳̋̓ͩ͒̓̒͜͝ ̷͋͢͏̬̤̼T̸̯̞̥ͤ̽͛̈̎̚͜ȟ̨̌͋͏̲͚̪̩͚̺͖̠é̻̰̞̣̍̕͟ ̧̩͔̥̘͓̘̽̂͑̏ͣ͑̓̃͝N̬̙͈̗͍̣̻̓́ͨͫͮ͘͜͡e͍̜̠͓̹̙͓̱͑͡z̵̙̦̳̲͓ͭ̑ͮ̀p͒͐҉̹͎̱̯̰͜ȩ̨̗̝͓̥̳̣̈̽ͧ͋̎́͑ͯ̚͞r̮̖̟̆ͩḑ͍͉͚̪̲̭͈̮ͮͬͣͭ̽̐̄̓̑́͜i̶̪͎̹̰̭͎͋͗ͧ͌̎͛͜͢a͉̦͇̖͓̰ͣͭ̾͗n̮̞̣̝̤̤͔̎̊͜ ̧̗͐̃̊͂͢h̴͙̳͉̺͕͌̉ͫ͐͒̋͊i̢̳͓̤̖͎̼ͤ̃̓ͫ̐ͬ̆͌̕͢ṽ͎͉̳̭̭̠̠̬̠͂͐͊̾͊ȩ̣̺̖̒̏̌͠-̛͕̼̞͌͑ͣͨͩ̃̒͢m̶̱̣̥̥̭̉̿ͩͧ̓͛̚ͅi̢͍̙̠ͩ͐̏n̹̩̬͓̬̦̲̈́̉͊̐̎d̨̧̛̤̭̯̥͓ͧ̒ͥ ̞̙̮͌ͫͬͪͤ̌ợ̫̏̋͋͒̈̀f̶̳̿̀̊͐ͅ ̑͘҉̱̯̤̘͕̺͡c̢̭̭̜̲̙̥͊̓ͤ̍ͨ́ẖ̫̖̆̃ͪ̌ͭ͞ä̷̫̺̩̘̪͍́ͤͫͫ̒ͦ͆͂͠͡o̥̖̥͚̾̋͋͊ͨ̆ͅs̘͉͔̲̫̪͕̠̟ͯ̒͋ͦ̒͢.̣̦̦̞ͮͬͩ ̰̦̤̞̹̮̟ͩ̓̂̓̉͒̏ͫ͢Z̎́̉͘͏̗̮a̧͌͋̂͛̏͏͏̣̩͍̞l̛̟̥͎ͨ͒̐ͤ͛ͅg̰̣ͫͣ̂̋͊ô̷̶͕̩͎̳̻̣̯̘̋̊̅ͧ̏ͫ.̴̮̯̺̻̻̣̻̣̗̿ͯ͒ ̹̮̮̱͖̫̝̋ͥ͆̌͛ͬ͌̄͗͟H̢̅҉̘̠̻e̷͊͊͋ͪ̑҉̮̻̬̞̖̖̭̩̩̕ ̬̪̍͜ͅw̴̧̳͓͓̤̤ͮ̍ͨ͒͜ͅh̳̱ͪ͋ͦ͗o͚͎̭͎͍̺̽ͣͦͅ ̣͙͊̑ͣ̄W͍͔̻͉̲̹͇̼̑̇ͥ̔̎ͮ̚͟a̫̞ͪ̔͘͜į̷̶͔͍̰͙̖̻̲ͯ̓̄͌̄̒̔̆t̷͚͓̼̼̔̈̄̀̚sͭ̎͛ͨ͏̼̻̗͚̼̫ ̵̨̦ͪ͂̂B͂̈́҉̸͎̩͓e͌͂҉̤͕̲͇̮h̴̤͎̟̫̐̀̐ͬį̖̪̜̦̋̔n̨̯͚̽͗̾̀̾̿̏̀d̙͔ͬͧ̃ͯ̀ͦͫ͌ ̸̮͓͎̣̻̪̹̒̈́ͧ̀͐̓̿͘͠T̮͎̫̝ͫ̔͛̈ͯ̈ͬͣ̈́͟h̲̉̆̀e̬̭ͧ̉ͮ̓ͥ̈́ͨ ̉̆̏͠͏̖̯͚̰W͎̞͕̺ͣ̉̓ͧ̎̽͟a̢̝̝̎̅̌̂ͦ͡ḽ͖͉̽ͥ̌̓̉̆l̠̣̾ͣ̾͛̕.̷̡̩̰̀̑͑̽͋̃̌̓ ̴͙̼̭̺̙̱͚̳̪ͨ̈́́Z̵̶̲̘̗̩̜̍ͭ̀̿͒̊ͫA̴̸ͧ̊̚҉̺͖̠͖̜̠̩͇L̶̲̠̾͗ͦ͐͌ͯͤ̇G̫̞͔̭̻̖̥̜̗͊ͪͦͧ̔ͩ̀͘͜Õ̷͉͈̖̭̰̲̪̾ͭͯ͆̚



In case your browser doesn't render it correctly, here's an image:

zalgo text

And it's not that hard to create it, as there are many generators available.

Although it doesn't look like regular ("normal") text, it kinda is - you can copy-paste it normally (if it'll be correctly displayed, it depends on the editor you're using).

But how does it work? How is it created, and how can I detect it and prevent my application from accepting inputs like this?

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Why? (3 comments)
Why?
H_H‭ wrote 11 months ago

Why do you want to prevent your users from using it? I mean, you already accept unicode, with support for many many languages (including different text directions, emoji, ...), why stop this form of text?

hkotsubo‭ wrote 11 months ago

H_H‭ It depends on what data the application considers "valid". If I want to be very strict and allow, let's say, only "valid text in a specific set of languages" (or anything closer to that), preventing zalgo text would be a good start, as it wouldn't allow lots of non-sense gibberish (it won't prevent all, of course, people can be very creative in that matter).

Just because I accept Unicode, it doesn't mean that I have to accept every possible combination of all existent characters. Each application can have its own restrictions on input data, YMMV.

H_H‭ wrote 11 months ago

Doesn't answer the question: Why do you want to prevent zalgo text?

Do you restrict other characters? Which one? Or do you have a whitelist? Why do you prevent other characters?

The answer can vary a lot depending on the why and what you already do.