Javascript-based "Tools"
These are simpler tools I use myself. Since the javascripts run from here, on my site, it means dynamic functionality is performed on the client side, that is, in your browser. This is sometimes seen as a disadvantage, but in these cases, it is actually the point, since it means what you do does not get sent over the internet, but stays in the browser. This is especially true if you have a more privacy aware browser, like LibreWolf, Mullvad or Brave.
Base 64
Base 64 Encoder: Write your text in the left box and the encoded text appears in the right, which you can copy into various messages.
Base 64 Decoder: Paste the encoded text string in the left box and the clear text appears in the right.
Base 64 Writer (large): The same as the Encoder above, only the writing box is larger for longer messages or those with structure.
Base 64 Decoder (large): Simply the larger version of the decoder.
About Base 64
Base 64 is encoding, not encryption. This means that anyone can convert back and forth between plaintext and the encoded text string.
It's something you actually use daily, since your email gets encoded to Base 64 by your mail program and decoded by the recipient's. One thing with this encoding is that it gives you one long string, but it actually keeps the structure of your message as well.
I use it if I write messages in a non-English language that will be encrypted using the older, basic GnuPG 1.4 package, since special language characters often broke when the message was moved between different software.
Examples of these characters would be Δ λ π å æ ð ¿. Using Base 64, you can even send runes to each other. (See below)
Another use is for passwords, unless you let your password manager create them randomly. For instance
"correct horse battery staple" would become "Y29ycmVjdCBob3JzZSBiYXR0ZXJ5IHN0YXBsZQ==", Base 64 generated.
(For the fan, the first is 28 characters long with an entropy of 70.88 bit, whereas the second is 40 characters long with an entropy of 224.31 bit.)
Norse Runes (Elder Futhark) in Base 64
If you decode this string, you should get the full runic alphabet in clear text:
UlVORVMNCuGaoCDhmqIgw74g4ZqoIOGasSDhmrIg4Zq3IOGauSANCuGauiDhmr4g4ZuB
IOGbgyDhm4gg4ZuHIOGbiSDhm4ogIA0K4ZuPIOGbkiDhm5Yg4ZuXIOGbmiDhm5wg4Zue
IOGbnw0KDQpmIHUgw74gYSByIGsgZyB3IA0KaCBuIGkgaiBwIGUvw68gUi96IHMgDQp0
IGIgZSBtIGwgxYsgZCBvDQoNCnM6IOGbiiBvciDhm4s=
OTP Encryption/Decryption (One Time Pad)
This is IMHO one of the cooler encryption methods. you don't even need a computer! OK, if you do it by hand, it will take longer time, but still doable. Wikipedia has an article about OTP. You can also find several videos explaining it on YouTube, that are probably easier to digest than that article.
OTP can use either letters or numbers. This OTP script uses letters.
Encryption/Decryption: Don't forget to switch the drop down from either Encrypt or Decrypt.
NOTE that this tool does not create a key for you, that one you have to provide for yourself. Though one way of quickly creating a key is using the Random Letter Sequence Generator below. Just remember that these are not true, advanced random generators, for that you need some serius hardware stuff. It should work for your purposes, as long as you don't send anything really classified and seriously secret.
Random Letter Sequence Generator
Generator: This can be used to create any kind of random text strings. You can even use it to roll two six-sided dice several times by adding the values 'Length of each random letter sequence': 2 and 'Letters to choose from': 123456.
Bottom left you have different strings to paste into the field 'Letters to choose from'. If you alternate between more than one and also click 'Click to generate letter sequences' more than once, you at least increase the entropy in your final sequence.