Text and word tools
Wordplay and witty texts is one of the oldest forms of puzzles. Anagrams have been traced to the time of the Ancient Greeks, and they still are popular in modern brain teasers. Synonyms are common not only in crosswords, but plays a role in a wider range of puzzles. This section also contains text processing tools, which are useful for reversing, changing case, etc of texts.
Computers and digital devices need to represent letters in appropriate ways. ASCII codes are very common for storing texts, but with the demand to support more non-English texts, the popularity of Unicode is increasing. Hashes are not encodings, but since they are more or less unique for all words, they can be considered like encodings (although much more difficult to reverse).
Ciphers and encryption
In cryptography, a cipher (or cypher) is a method for protecting data through encryption and decryption. Most ciphers require a specific key for encryption and decryption, but some ciphers like the ROT13 or Atbash ciphers have fixed keys. Most of the ciphers listed here are classic ciphers that were popular during an earlier time, but today mostly are used only by puzzle makers.
While encryption protects information from being understood, an even higher protection would be if the information is hidden. The word steganography comes from the Greek word "steganos", meaning concealed, and "graphein", meaning writing. Modern steganography can hide information in images and audio files. Also information can be manually hidden in images through the use of very low contrast colors or metadata.
Mathematics play an important role in logic puzzles and code-breaking. It is important to be able to convert between different number systems, and detect special properties of numbers such as that they are prime numbers. Also number sequences, like the Fibonacci sequence, are commonly used in puzzles.
Every alphabet has a number of symbols that are the building blocks of the specific language. In addition to traditional written languages, alphabets have evolved for telegraphy (Morse code), visually impaired people (Braille) and maritime signal flags. Further alphabets have evolved in popular culture, such as the Klingon alphabet (from Star Trek) or dancing men code (from Sherlock Holmes).
You can't rely on tools only
Although tools can be helpful, there's a saying: "A fool with a tool is still only a fool". Good quality code-breaking puzzles can't be solved simply by using tools. It's your wits and creativity that matter, and the tools are just there to help explore your ideas.