String APIs provided by @justyy (APIs may be rate limited, NOT to be used for Production, Use it at your own risk)
  
  - jaccard similarity between two strings
  GET: https://str.justyy.workers.dev/jaccard/?s=this+is+a+book|that+is+a+car
  POST: curl -s -X POST --data "This is a car | that is a book" "https://str.justyy.workers.dev/jaccard/"
  PUT: curl -s -X PUT --data "This is a car | that is a book" "https://str.justyy.workers.dev/jaccard/"

  - sudoku solver
curl -s -X POST "https://str.justyy.workers.dev/sudoku/" -d "000002000
000030016
000947300
002400800
061000007
405000000
009200074
020000103
030010960"
Returns:
[["8","4","3","1","6","2","7","9","5"],["2","9","7","8","3","5","4","1","6"],["1","5","6","9","4","7","3","2","8"],["3","7","2","4","9","6","8","5","1"],["9","6","1","3","5","8","2","4","7"],["4","8","5","7","2","1","6","3","9"],["6","1","9","2","8","3","5","7","4"],["5","2","4","6","7","9","1","8","3"],["7","3","8","5","1","4","9","6","2"]]  

Add Query parameter ?format=raw to format output as RAW text
843162795
297835416
156947328
372496851
961358247
485721639
619283574
524679183
738514962

Also, you can invoke the API via PUT.

  - hex string to ascii
  GET: https://str.justyy.workers.dev/hex/?s=524556455254206f70636f6465206578656375746564
  POST: curl -s -X POST --data "524556455254206f70636f6465206578656375746564" "https://str.justyy.workers.dev/hex/"
  PUT: curl -s -X PUT --data "524556455254206f70636f6465206578656375746564" "https://str.justyy.workers.dev/hex/"

  - rot13 cipher
  GET: https://str.justyy.workers.dev/rot13/?s=Hello
  POST: curl -s -X POST -d "Hello" "https://str.justyy.workers.dev/rot13/"
  PUT: curl -s -X PUT -d "Hello" "https://str.justyy.workers.dev/rot13/"

  - rot47 cipher
  GET: https://str.justyy.workers.dev/rot47/?s=Hello
  POST: curl -s -X POST -d "Hello" "https://str.justyy.workers.dev/rot47/"
  PUT: curl -s -X PUT -d "Hello" "https://str.justyy.workers.dev/rot47/"

  - atob (Base64 Decode)
  GET: https://str.justyy.workers.dev/atob/?s=SGVsbG8sIFdvcmxkIQ==
  POST: curl -s -X POST -d "SGVsbG8sIFdvcmxkIQ==" "https://str.justyy.workers.dev/atob/"
  PUT: curl -s -X PUT -d "SGVsbG8sIFdvcmxkIQ==" "https://str.justyy.workers.dev/atob/"

  - btoa (Base64 Encode)
  GET: https://str.justyy.workers.dev/btoa/?s=Hello
  POST: curl -s -X POST -d "Hello" "https://str.justyy.workers.dev/btoa/"
  PUT: curl -s -X PUT -d "Hello" "https://str.justyy.workers.dev/btoa/"

  - md5 hashing
  GET: https://md5.functionapi.workers.dev/?s=Hello
  POST: curl -s -X POST -d "Hello" "https://md5.functionapi.workers.dev"  
  PUT: curl -s -X PUT -d "Hello" "https://md5.functionapi.workers.dev"  

  - echo
  GET: https://str.justyy.workers.dev/echo/?s=Hello
  POST: curl -s -X POST -d "Hello" "https://str.justyy.workers.dev/echo/"
  PUT: curl -s -X PUT -d "Hello" "https://str.justyy.workers.dev/echo/"
  
  - random-user-agent
  GET: https://str.justyy.workers.dev/random-user-agent/
  POST: curl -s -X POST -d "Hello" "https://str.justyy.workers.dev/random-user-agent/"
  PUT: curl -s -X PUT -d "Hello" "https://str.justyy.workers.dev/random-user-agent/"

  Please contact me justyy@zoho.com to report bugs or provide suggestions!
   
  To support @justyy, please vote him as a steem witness, thank you!
    https://steemyy.com/witness-voting/?witness=justyy&action=approve
  
  Buy Me a Coffee: https://www.buymeacoffee.com/y0BtG5R