The MD5 hash cannot be decrypted if the text you entered is complicated enough.
The MD5 message summary algorithm is a widely used hash function that produces a 128-bit hash value. Although MD5 was initially designed to be used as a cryptographic hash function, it has been found to suffer from extensive vulnerabilities. It can still be used as a checksum to verify the integrity of the data, but only against involuntary corruption. It is still suitable for other non-cryptographic purposes, for example, to determine the partition of a particular key in a partitioned database.
The MD5 was designed by Ronald Rivest in 1991 to replace an earlier MD4 hash function, and was specified in 1992 as RFC 1321.
A basic requirement of any cryptographic hash function is that it should not be computationally feasible to find two different messages that have the same value. MD5 fails this requirement catastrophically; Such collisions can be found in seconds on an ordinary home computer.
The weaknesses of MD5 have been exploited in the field, most infamously by Flame malware in 2012. The CMU Software Engineering Institute believes that MD5 is essentially "cryptographically broken and unsuitable for later use."
As of 2019, MD5 continues to be widely used, despite its well-documented weaknesses and depreciation by security experts.