The Ensembl Pre! site was launched in 2003 to provide early access to preliminary data generated during the gene annotation process.
Genome sequences and preliminary data were made available in the Pre! site, prior to full annotation and integration into Ensembl. Pre! data allowed researchers to get a head start on analysing the genome prior to its integration into Ensembl.
In recent years, the optimisation of the Ensembl gene annotation process means that the complete genebuild for a newly sequenced genome can take days rather than months. And with the huge increase in sequencing being performed by large biodiversity initiatives such as Darwin Tree of Life, the Vertebrate Genomes Project and the Earth BioGenome Project, Ensembl recently launched the Rapid Release site to provide annotation for these recently produced, high quality and publicly available genomes as quickly as possible.
With full, high-quality gene annotation being made available through the Rapid Release site with greater levels of functionality, the Pre! site has become redundant and will be formally retired on the 31st January 2021.
Ensembl Rapid Release site referred above is here: https://rapid.ensembl.org/index.html