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Foldseek enables fast and sensitive comparisons of large structure sets.


van Kempen M, Kim S, Tumescheit C, Mirdita M, Söding J, and Steinegger M. Foldseek: fast and accurate protein structure search. bioRxiv, doi:10.1101/2022.02.07.479398 (2022)

Tutorial Video

We presented a Foldseek tutorial at the SBGrid where we demonstrate the webserver and command line interface of foldseek. Check it out here.



Search your protein structures against the AlphaFoldDB and PDB in seconds using our Foldseek webserver: 🚀


# static Linux AVX2 build (check using: cat /proc/cpuinfo | grep avx2)
wget; tar xvzf foldseek-linux-avx2.tar.gz; export PATH=$(pwd)/foldseek/bin/:$PATH
# static Linux SSE4.1 build (check using: cat /proc/cpuinfo | grep sse4_1)
wget; tar xvzf foldseek-linux-sse41.tar.gz; export PATH=$(pwd)/foldseek/bin/:$PATH
# static macOS build (universal binary with SSE4.1/AVX2/M1 NEON)
wget; tar xvzf foldseek-osx-universal.tar.gz; export PATH=$(pwd)/foldseek/bin/:$PATH
# conda installer 
conda install -c conda-forge -c bioconda foldseek

Other precompiled binaries for ARM64, PPC64LE amd SSE2 are available at

Quick start

easy-search can search single or multiple query structures formatted in PDB/mmCIF format (flat or .gz) against a target database (example/) of protein structures. It outputs a tab-separated file of the alignments (.m8) the fields are query,target,fident,alnlen,mismatch,gapopen,qstart,qend,tstart,tend,evalue,bits.

foldseek easy-search example/d1asha_ example/ aln.m8 tmpFolder

Output: Customize fields of tab seperated output

The output can be customized with the --format-output option e.g. --format-output "query,target,qaln,taln" returns the query and target accession and the pairwise alignments in tab separated format. You can choose many different output columns.

query       Query sequence identifier 
target      Target sequence identifier
evalue      E-value
gapopen     Number of gap open events (note: this is NOT the number of gap characters)
pident      Percentage of identical matches
fident      Fraction of identical matches
nident      Number of identical matches
qstart      1-indexed alignment start position in query sequence
qend        1-indexed alignment end position in query sequence
qlen        Query sequence length
tstart      1-indexed alignment start position in target sequence
tend        1-indexed alignment end position in target sequence
tlen        Target sequence length
alnlen      Alignment length (number of aligned columns)
raw         Raw alignment score
bits        Bit score
cigar       Alignment as string. Each position contains either M (match), D (deletion, gap in query), or I (Insertion, gap in target)
qseq        Query sequence 
tseq        Target sequence
qaln        Aligned query sequence with gaps
taln        Aligned target sequence with gaps
qheader     Header of Query sequence
theader     Header of Target sequence
mismatch    Number of mismatches
qcov        Fraction of query sequence covered by alignment
tcov        Fraction of target sequence covered by alignment
empty       Dash column '-'
taxid       Taxonomical identifier (needs mmseqs tax db)
taxname     Taxon Name (needs mmseqs tax db)
taxlineage  Taxonomical lineage (needs mmseqs tax db)
qset        Query filename of FASTA/Q (useful if multiple files were passed to createdb)
qsetid      Numeric identifier for query filename
tset        Target filename of FASTA/Q (useful if multiple files were passed to createdb)
tsetid      Numeric identifier for target filename
qca         Calpha corrdinates of the query
tca         Calpha corrdinates of the target
alntmscore  TM-score of the alignment 
qtmscore    TM-score normalized by the query length
ttmscore    TM-score normalized by the target length
u           Rotation matrix (computed to by TM-score)
t           Translation vector (computed to by TM-score)
lddt        Average LDDT of the alignment    
lddtfull    LDDT per aligned position

Output: Superpositioned Cα only PDB files

Foldseek's --format-mode 5 generates PDB files with all Cα atoms superimposed based on the aligned coordinates on to the query structure. For each pairwise alignment it will write a single PDB files, so be carefull when using this options for large searches.

Create reusable databases and indexes

The target database can be pre-processed by createdb. This make sense if searched multiple times.

foldseek createdb example/ targetDB
foldseek createindex targetDB tmp  #OPTIONAL generates and stores the index on disk
foldseek easy-search example/d1asha_ targetDB aln.m8 tmpFolder

Important search parameters

# sensitivity and speed
-s                       adjust the sensitivity to speed trade-off.
                         lower is faster, higher more sensitive (fast: 7.5, highest sensitivity (default): 9.5)
--exhaustive-search      skips the prefilter and performs an all-vs-all alignment (more sensitive but much slower)                         
--max-seqs               adjust the amount of prefilter that are handed to the alignment. 
                         Increasing it can lead to more hits (default: 1000)
-e                       List matches below this E-value (range 0.0-inf, default: 0.001)
                         Increasing it helps to report more distantly related structures.
                         Structures with an E-value of up to 1 might be still related.
# other                         
--alignment-type         0: 3Di Gotoh-Smith-Waterman (local, not recommended), 
                         1: TMalign (global, slow), 
                         2: 3Di+AA Gotoh-Smith-Waterman (local, default)
-c                       list matches above this fraction of aligned (covered) residues (see --cov-mode) (default: 0.0) 
                         The higher the alignment coverage the more global is the alignment.
--cov-mode               0: coverage of query and target, 1: coverage of target, 2: coverage of query


The databases command downloads pre-generated databases like PDB or AlphaFoldDB.

# pdb  
foldseek databases PDB100 pdb tmp 
# alphafold db
foldseek databases Alphafold/Proteome afdb tmp 

We currently support the following databases:

  Name                   	Type     	Taxonomy	Url
- Alphafold/UniProt   	Aminoacid	     yes
- Alphafold/UniProt50 	Aminoacid	     yes
- Alphafold/Proteome  	Aminoacid	     yes
- Alphafold/Swiss-Prot	Aminoacid	     yes
- ESMAtlas30          	Aminoacid	       -
- PDB                 	Aminoacid	     yes

Main Modules

  • easy-search fast protein structure search
  • createdb create a database from protein structures (PDB,mmCIF, mmJSON)
  • databases download pre-assembled databases

Using TMalign for the alignment

Foldseek supports to realign hits using TMalign as well as rescoring alignments using TMscore.

foldseek easy-search example/d1asha_ example/ aln tmp --alignment-type 1

In case of the alignment type (--alignment-type 1) tmalign we sort the results by the TMscore normalized by query length. We write the TMscore into the e-value(=TMscore) as well as into the score(=TMscore*100) field.

Rescore aligments using TMscore

Easiest way to get the alignment TMscore normalized by min(alnLen,qLen,targetLen) as well as a rotation matrix is through the following command:

foldseek easy-search example/ example/ aln tmp --format-output query,target,alntmscore,u,t

Alternative, it is possible to compute TMscores for the kind of alignment output (e.g. 3Di/AA) using the following commands:

foldseek createdb example/ targetDB
foldseek createdb example/ queryDB
foldseek search queryDB targetDB aln tmpFolder -a
foldseek aln2tmscore queryDB targetDB aln aln_tmscore
foldseek createtsv queryDB targetDB aln_tmscore aln_tmscore.tsv

Output format aln_tmscore.tsv: query and target identifier, TMscore, translation(3) and rotation vector=(3x3)

Search result visualisations

Foldseek can locally generate a search result HTML similiar to the webserver by specifying the format mode --format-mode 3

foldseek easy-search example/d1asha_ example/ result.html tmp --format-mode 3

Cluster structures

The following command aligns the input structures all-against-all and keeps only alignments with 80% of the sequence covered by the alignment (-c 0.8) (read more about alignment coverage here). It then clusters the results using greedy set cover algorithm. The clustering mode can be adjusted using --cluster-mode, read more here. The clustering output format is described here.

foldseek createdb example/ db
foldseek search db db aln tmpFolder -c 0.8 
foldseek clust db aln clu
foldseek createtsv db db clu clu.tsv

Query centered multiple sequence alignment

Foldseek can generate a3m based multiple sequence alignments using the following commands. a3m can be converted to fasta format using ( in.a3m out.fas).

foldseek createdb example/ targetDB
foldseek createdb example/ queryDB
foldseek search queryDB targetDB aln tmpFolder -a
foldseek result2msa queryDB targetDB aln msa --msa-format-mode 6
foldseek unpackdb msa msa_output --unpack-suffix a3m --unpack-name-mode 0

Compile from source

Compiling foldseek from source has the advantage of system-specific optimizations, which should improve its performance. To compile it git, g++ (4.9 or higher) and cmake (3.0 or higher) are required. Afterwards, the foldseek binary will be located in the build/bin directory.

git clone
cd foldseek
mkdir build
cd build
make -j
make install
export PATH=$(pwd)/foldseek/bin/:$PATH

If you want to compile foldseek on macOS, please install and use gcc from Homebrew. The default macOS clang compiler does not support OpenMP (by default) and foldseek will not be able to run multi-threaded. Adjust the cmake call above to:

CC="$(brew --prefix)/bin/gcc-11" CXX="$(brew --prefix)/bin/g++-11" cmake -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_INSTALL_PREFIX=. ..