Release Notes and Known Bugs

The WebLogo release notes detail changes to WebLogo and known issues with particular versions.


WebLogo is a web based application designed to make the generation of sequence logos as easy and painless as possible.

A sequence logo is a graphical representation of an amino acid or nucleic acid multiple sequence alignment. Each logo consists of stacks of symbols, one stack for each position in the sequence. The overall height of the stack indicates the sequence conservation at that position, while the height of symbols within the stack indicates the relative frequency of each amino or nucleic acid at that position. The width of the stack is proportional to the fraction of valid symbols in that position. (Positions with many gaps have thin stacks.)In general, a sequence logo provides a richer and more precise description of, for example,a binding site, than would a consensus sequence.


Crooks GE, Hon G, Chandonia JM, Brenner SE WebLogo: A sequence logo generator, Genome Research, 14:1188-1190, (2004) [ Full Text ]

Schneider TD, Stephens RM. 1990. Sequence Logos: A New Way to Display Consensus Sequences. Nucleic Acids Res. 18:6097-6100

Creating Sequences Logos using the Web interface

Sequence Data
Enter your multiple sequence alignment or position weight matrix file, or select a file to upload. Supported file formats include CLUSTALW, FASTA, plain flatfile, MSF, NBRF, PIR, NEXUS and PHYLIP for multiple sequence alignments, and transfac for position weight matrices. All sequences must be the same length, else WebLogo will return an error and report the first sequence that differed in length from previous sequences.

Output format
Generally speaking, vector formats (EPS and PDF) are better for print, while bitmaps (JPEG and PNG) are more suitable for displaying on the screen or embedding into a web page.
PNG: (600 DPI) Print resolution bitmap
PNG: (low res, 96 DPI) Screen resolution bitmap
JPEG: Screen resolution bitmap
EPS: Encapsulated postscript
PDF: Portable Document Format
SVG: Scalable Vector Graphics

Logo size
The physical dimensions of the generated logo. Specifically, Logo Size controls the size of individual symbols stacks.
small: 5.4 points wide (same as 9pt Courier), aspect ratio 5:1
medium: Double the width and height of small.
large: Triple the width and height of small.
The choices have been limited to promote inter-logo consistency. Small logos can fit 80 stacks across a printed page, or 40 across a half page column. The command line interface provides greater control, if so desired.

Stacks per line
If the length of the sequences is greater than this maximum number of stacks per line, then the logo will be split across multiple lines.

Sequence Type
Selects the type of biological molecule.
auto: Automatically guess sequence type from the data

Ignore Lower Case
Disregard lower case letters and only count upper case letters in sequences

The units used for the y-axis.
probability: Show residue probabilities, rather than information content. If compositional adjustment is disabled, then these are the raw residue frequencies.
bits: Information content in bits
nats: Natural units, 1 bit = ln 2 (0.69) nats
kT: Thermal energy units in natural units (numerically the same as nats)
kJ/mol: Thermal energy (assuming T = 300 K)
kcal/mol: Thermal energy (assuming T = 300 K)

First position number
The numerical label of the first position in the sequence data in the input file. The label must be an integer. Residue labels for the logo will be relative to this number. (See also: Logo range.)

Logo range
By default, all sequence data from the input file is displayed in the Sequence Logo. With this option, you can instead show a subrange of the sequence data. The numbering of Start and End Positions is relative to the First Position Number. Thus, if the First Position Number is "2", Start is "5" and End is "10", then the 4th through 9th (inclusive) sequence positions of the input file will be displayed, and they will be numbered "5", "6", "7", "8", "9" and "10".


The background composition of the genome or proteome from which the sequences have been drawn. The default, automatic option is to use equiprobable background for nucleic acids and a typical amino acid usage pattern for proteins. However, you may also explicitly set the expected CG content for nucleic acid sequences, insist on equiprobable background distributions, or turn off composition adjustment altogether.

Compositional adjustment has two effects. First, the information content of a site is defined as the relative entropy of the monomers at that site to the background distribution. Consequentially, rare monomers have higher information content (when they occur) than relatively common monomers.

Secondly, the background composition is used in the small sample correction of information content. Briefly, if only a few sequences are available in the multiple sequence alignment, then sites typically appear more conserved than they really are. Small samples bias the relative entropy upwards. To compensate, we add pseudocounts to the actual counts, proportional to the expected background composition. These pseudocounts smooth the data for small samples, but become irrelevant for large samples. The proportionality constant is set to 4 for nucleic acid sequences, and 20 for proteins (these numbers have been found to give reasonable results in practice).

Behind the scenes, things are more complex. We do a full Bayesian calculation, starting with explicit Dirichlet priors based on the background composition, to which we add the data and then calculate both the posterior mean relative entropy (the stack height) and Bayesian 95% confidence intervals for error bars. These interesting details will be explained elsewhere.

Scale stack width
Scale the visible stack width by the fraction of symbols in the column.(I.e. columns with many gaps or unknown residues are narrow.)

Error bars
Display error bars. These indicate an approximate Bayesian 95% confidence interval.

Give your logo a title.

Figure label
An optional figure label, added to the top left (e.g. '(a)').

Add a label to the x-axis, or hide axis altogether.

The vertical axis indicates the information content of a sequence position. Use this option to toggle the y-axis and override the default axis label.

Y-axis scale
The height of the y-axis in designated units. The automatic option will pick reasonable defaults based on the sequence type and axis unit.

Y-axis tic spacing
The distance between major tic marks on the y-axis.

Sequence end labels
Choose this option to label the 5' & 3' ends of nucleic acid or the N & C termini of amino acid sequences.

Version fineprint
Toggle display of the WebLogo version information in the lower right corner. Optional, but we appreciate the acknowledgment.

Color Scheme
Use Base Pairing for nucleic acids (NA), Hydrophobicity for amino acids (AA).

All symbols black

Base Pairing
(NA default):
2 Watson-Crick hydrogen bonds TAU dark orange
3 Watson-Crick hydrogen bonds GC blue

Classic (NA):
G orange
TU red
C blue
A green
WebLogo (version 1 and 2) and makelogo default color scheme for nucleic acids: G, orange; T & U, red; C, blue; and A, green.

(AA default):
Hydrophilic RKDENQ blue
Neutral SGHTAP green
Hydrophobic YVMCLFIW black

Chemistry (AA):
Color amino acids according to chemical properties.
Polar G,S,T,Y,C green
Neutral Q,N purple
Basic K,R,H blue
Acidic D,E red
Hydrophobic A,V,L,I,P,W,F,M black
WebLogo (version 1 and 2) and makelogo default color. (Note that the WebLogo 2 documentation erroneously lists Q and N under green.)

Charge (AA) :
Positive KRH blue
Negative DE red

A custom color scheme can be specified in the input field below. Specify colors on the left and associated symbols on the right. Colors are entered using CSS2 (Cascading Style Sheet) syntax. (E.g. 'red', '#F00', '#FF0000', 'rgb(255, 0, 0)', 'rgb(100%, 0%, 0%)' or 'hsl(0, 100%, 50%)' for the color red.)

More Options
The weblogo command line client, weblogo, provides many more options and greater control over the final logo appearance.

Installing WebLogo


WebLogo version 3 is written in python. It is necessary to have Python 3.7 or later and the extension package numpy installed before WebLogo will run. WebLogo also requires a recent version of ghostscript to create PNG and PDF output, and pdf2svg to generate SVG output.

Download and Installation

WebLogo and its dependencies can be downloaded and installed with pip,
                pip install weblogo
or conda.
                conda install -c conda-forge weblogo
Alternatively, weblogo and its dependencies can be installed manually. The WebLogo source code can be downloaded from Weblogo's Github repository. This code is distributed under various open source licenses. Please consult the LICENSE.txt file in the source distribution for details.

After unpacking the WebLogo tarfile, it should be possible to immediately create logos using the command line client (provided that python, numpy and ghostscript have already been installed).

                ./weblogo --format PNG < cap.fa > cap.png   

Please consult the file for more examples.

To run WebLogo as a stand alone web service, run the logo server command :

                ./weblogo --serve 

It should now be possible to access WebLogo at http://localhost:8080/.

Web App

To use WebLogo as a web application, first install the weblogo dependencies and libraries as above, then place (or link) the weblogo/htdocs directory somewhere within the document root of your webserver. The webserver must be able to execute the CGI script create.cgi. For Apache, you may have to add an ExecCGI option and add a cgi handler in the httpd.conf configuration file. Something like this:
                    DocumentRoot "/home/ec2-user/weblogo/weblogo/htdocs"

                    # Further relax access to the default document root:
                    <Directory "/home/ec2-user/weblogo/weblogo/htdocs">
                        Options Indexes FollowSymLinks ExecCGI MultiViews
                        AddHandler cgi-script .cgi
                        AllowOverride All
                        Require all granted

It may also be necessary to set the PATH and PYTHONPATH environment variables.
                    SetEnv PYTHONPATH /path/to/weblogo/libraries
The cgi script also has to be able to find the 'gs' ghostscript executable. The maximum bytes of uploaded sequence data can be controlled with the WEBLOGO_MAX_FILE_SIZE environment variable.
                    SetEnv WEBLOGO_MAX_FILE_SIZE 1000000

weblogo, The WebLogo Command Line Interface (CLI)

The command line client has many options not available through the web interface. Please consult the bundled script for inspiration.
Usage: weblogo [options]  < sequence_data.fa > sequence_logo.eps

Create sequence logos from biological sequence alignments.

     --version                  show program's version number and exit
  -h --help                     show this help message and exit

  Input/Output Options:
    -f --fin FILENAME           Sequence input file (default: stdin)
       --upload URL             Upload input file from URL
    -D --datatype FORMAT        Type of multiple sequence alignment or
                                position weight matrix file: (clustal, fasta,
                                msf, genbank, nbrf, nexus, phylip, stockholm,
                                intelligenetics, table, array, transfac)
    -o --fout FILENAME          Output file (default: stdout)
    -F --format FORMAT          Format of output: eps (default), png,
                                png_print, pdf, jpeg, svg, logodata

  Logo Data Options:
    -A --sequence-type TYPE     The type of sequence data: 'protein', 'rna' or
    -a --alphabet ALPHABET      The set of symbols to count, e.g. 'AGTC'. All
                                characters not in the alphabet are ignored. If
                                neither the alphabet nor sequence-type are
                                specified then weblogo will examine the input
                                data and make an educated guess. See also
                                --sequence-type, --ignore-lower-case
    -U --units UNIT             A unit of entropy ('bits' (default), 'nats',
                                'digits'), or a unit of free energy ('kT',
                                'kJ/mol', 'kcal/mol'), or 'probability' for
       --composition COMP.      The expected composition of the sequences:
                                'auto' (default), 'equiprobable', 'none' (do
                                not perform any compositional adjustment), a
                                CG percentage, a species name (e.g. 'E. coli',
                                'H. sapiens'), or an explicit distribution
                                (e.g. "{'A':10, 'C':40, 'G':40, 'T':10}"). The
                                automatic option uses a typical distribution
                                for proteins and equiprobable distribution for
                                everything else.
       --weight NUMBER          The weight of prior data.  Default depends on
                                alphabet length
    -i --first-index INDEX      Index of first position in sequence data
                                (default: 1)
    -l --lower INDEX            Lower bound of sequence to display
    -u --upper INDEX            Upper bound of sequence to display

    Optional transformations of the sequence data.

       --ignore-lower-case      Disregard lower case letters and only count
                                upper case letters in sequences.
       --reverse                reverse sequences
       --complement             complement nucleic sequences
       --revcomp                reverse complement nucleic sequences

  Logo Format Options:
    These options control the format and display of the logo.

    -s --size LOGOSIZE          Specify a standard logo size (small, medium
                                (default), large)
    -n --stacks-per-line COUNT  Maximum number of logo stacks per logo line.
                                (default: 40)
    -t --title TEXT             Logo title text.
       --label TEXT             A figure label, e.g. '2a'
    -X --show-xaxis YES/NO      Display sequence numbers along x-axis?
                                (default: True)
    -x --xlabel TEXT            X-axis label
       --annotate TEXT          A comma separated list of custom stack
                                annotations, e.g. '1,3,4,5,6,7'.  Annotation
                                list must be same length as sequences.
       --rotate-numbers YES/NO  Draw X-axis numbers with vertical orientation
                                (default: False).
       --number-interval NUMBER
                                Distance between numbers on X-axis (default:
    -S --yaxis NUMBER           Height of yaxis in units. (Default: Maximum
                                value with uninformative prior.)
    -Y --show-yaxis YES/NO      Display entropy scale along y-axis? (default:
    -y --ylabel TEXT            Y-axis label (default depends on plot type and
    -E --show-ends YES/NO       Label the ends of the sequence? (default:
    -P --fineprint TEXT         The fine print (default: weblogo version)
       --ticmarks NUMBER        Distance between ticmarks (default: 1.0)
       --errorbars YES/NO       Display error bars? (default: True)
       --reverse-stacks YES/NO  Draw stacks with largest letters on top?
                                (default: True)

  Color Options:
    Colors can be specified using CSS2 syntax. e.g. 'red', '#FF0000', etc.

    -c --color-scheme SCHEME    Specify a standard color scheme (auto, base
                                pairing, charge, chemistry, classic,
                                hydrophobicity, monochrome)
                                Specify symbol colors, e.g. --color black AG
                                'Purine' --color red TC 'Pyrimidine'
       --default-color COLOR    Symbol color if not otherwise specified.

  Font Format Options:
    These options provide control over the font sizes and types.

       --fontsize POINTS        Regular text font size in points (default: 10)
       --title-fontsize POINTS  Title text font size in points (default: 12)
       --small-fontsize POINTS  Small text font size in points (default: 6)
       --number-fontsize POINTS
                                Axis numbers font size in points (default: 8)
       --text-font FONT         Specify font for labels (default: ArialMT)
       --logo-font FONT         Specify font for logo (default: Arial-BoldMT)
       --title-font FONT        Specify font for title (default: ArialMT)

  Advanced Format Options:
    These options provide fine control over the display of the logo.

    -W --stack-width POINTS     Width of a logo stack (default: 10.8)
       --aspect-ratio POINTS    Ratio of stack height to width (default: 5)
       --box YES/NO             Draw boxes around symbols? (default: no)
       --resolution DPI         Bitmap resolution in dots per inch (DPI).
                                (Default: 96 DPI, except png_print, 600 DPI)
                                Low resolution bitmaps (DPI<300) are
       --scale-width YES/NO     Scale the visible stack width by the fraction
                                of symbols in the column?  (I.e. columns with
                                many gaps of unknowns are narrow.)  (Default:
       --debug YES/NO           Output additional diagnostic information.
                                (Default: False)
       --errorbar-fraction NUMBER
                                Sets error bars display proportion (default:
       --errorbar-width-fraction NUMBER
                                Sets error bars width display proportion
                                (default: 0.25)
       --errorbar-gray NUMBER   Sets error bars' gray scale percentage
                                (default: 0.75)

  WebLogo Server:
    Run a standalone webserver on a local port.

       --serve                  Start a standalone WebLogo server for creating
                                sequence logos.
       --port PORT              Listen to this local port. (Default: 8080)

WebLogo Application Programmer Interface (API)

The WebLogo python libraries provide even greater flexibility than the command line client. Please consult the code documentation at readthedocs.

WebLogo Development and Future Features

The development project is hosted at If you wish to extend WebLogo or to contribute code, then you should download the full source code development package directly from the Github repository.

                > git clone
                > pip install -e .

                > cd weblogo

Please consult the developer notes, DEVELOPERS.txt and software license LICENSE.txt

Outstanding bugs and feature requests are listed on the WebLogo issue tracker.


WebLogo 2

The legacy WebLogo 2 sever can be found here.


WebLogo was created by Gavin E. Crooks, Liana Lareau, Gary Hon, John-Marc Chandonia and Steven E. Brenner. Many others have provided suggestions, bug fixes and moral support.

WebLogo was originally based upon the programs alpro and makelogo, both of which are part of Tom Schneider's delila package. Many thanks are due to him for making this software freely available and for encouraging its use.


While no permanent records are kept of submitted sequences, we cannot undertake to guarantee that data sent to WebLogo remains secure. Moreover, no guarantees whatsoever are provided about data generated by WebLogo.


Suggestions on how to improve WebLogo are heartily welcomed! Please direct questions to WebLogo's issue tracker.