Help items
File Menu Edit Menu Align Menu Props Menu Sites Menu Species Menu
Footers Menu Search Goto Trees Menu Alignment panel Tree windows
Dot plot Mase file format Program arguments Sequence coloring Miscellaneous options Customization
About seaview

Program seaview was published in:
Gouy, M. Guindon, S. & Gascuel., O. (2010) SeaView version 4 : a multiplatform graphical user interface for sequence alignment and phylogenetic tree building. Molecular Biology and Evolution 27(2):221-224.
Galtier, N., Gouy, M. & Gautier, C. (1996) SEAVIEW and PHYLO_WIN: two graphic tools for sequence alignment and molecular phylogeny. Comput. Appl. Biosci., 12:543-548.

Version 4.2.12

Binaries and full source code available from

(C) 1996-2009 Manolo Gouy
Laboratoire de Biometrie et Biologie Evolutive
CNRS / Universite Lyon I

Licensed under the GNU General Public Licence (

Seaview drives the Muscle, ClustalW2 and PhyML programs and uses code from the PHYLIP package for parsimony. Please quote:

Seaview uses the FLTK project ( for its user interface.

Some seaview versions use the PDFlib Lite library ( for pdf output under the "Open Source Developer Exemption" of the PDFlib Lite License Agreement.

Alignment panel

Mouse Use:

Active keys: Mouse use on the site line (when there is one, white line at bottom):
File Menu

Open, Open Mase, Open Phylip, Open Clustal, Open MSF, Open Fasta, Open NEXUS: to load an alignment in one of these formats. Formats Phylip, Clustal and Fasta use _ instead of space in names. Only the interleaved version of the Phylip format is supported. Mase and Nexus formats have the useful feature of allowing extra data beyond sequences and names (comments, accession numbers are really useful!). They can also store trees, site sets [see Sites Menu], species sets, footers, genetic code information.

Import from DBs: to import one or several sequences from databases (EMBL, GenBank, SwissProt/UniProt) into the alignment window naming them either by their ID or LOCUS record name or by their species. Sequences can be identified by two means:
1. By name, accession number or keyword. Protein IDs, without their extension (e.g., CAA06608 from /protein_id="CAA06608.1"), are processed as keywords attached to sequences, so can also be used. Because imported sequences are named with information taken from their ID/LOCUS record, the protein ID won't be used to name the sequence.
2. By a local text file of names or accession nos (one per line, strict text file, e.g., not a .doc or .odt file).
In case 1. and for nucleotide databases, it is also possible to import sequence fragments corresponding to a specified feature key (e.g., CDS, rRNA, tRNA) and, optionally, to require a given string to be present in the feature's annotations. If no matching string is specified, only the first matching feature key is imported. CDSs are imported with their correct genetic code and reading frame. Imports require an internet connection that allows outbound access to port # 5558. Access to a series of other databases is also possible.

Save: when active, saves the alignment in the current file (which name appears as window title). The shortcut for this operation is Ctrl-S (Cmd-S on Mac).

Save as...: to save the alignment under a name and a format to be chosen in the file selector appearing next.

Save selection: only active when some sequences are selected or when a site line is displayed; allows to save in a file selected sites, or selected sequences, or selected sites of selected sequences.

Save prot alignmnt: only active when a nucleotide alignment is translated to proteins; allows to save resulting protein sequences in any format.

Prepare pdf: Writes the alignment as a pdf file with optional choices set through the File/pdf options menu item or the file dialog on Mac OS:

Concatenate: To add one alignment (source) to the end of another (target). Can be done "by name" (seqs with same name are concatenated) or "by rank" (seqs with same rank in alignments are concatenated). Option "add gaps" replaces names absent in either alignment by gap-only sequences ("by name" only).

New window: Opens a new, empty alignment window.

Close window: Closes the alignment window.

Quit: guess what?

Edit Menu

Copy selected seqs: only active when some sequences are selected; copies in clipboard these sequences, or only their selected sites if a site line is displayed.
Paste alignment data: To paste previously copied alignment data to the end of the current alignment window.
Select all: Selects all sequences from the alignment.
Rename sequence: To rename the currently selected (= name in black background) sequence.
Edit comments: To see or change comments of the currently selected sequence (Comments can only be saved in mase/NEXUS formats).
Edit sequence: To edit the selected sequence, typically by pasting external data, or by opening two edit sequence windows and transferring sequence data between them.
Delete sequence(s): Deletes all selected sequences from the alignment.
Create sequence: Allows to create a new, empty sequence in the alignment; set "Allow seq. edition" from Props menu ON to be able to type the sequence in.
Load sequence: Allows to load a new sequence in the alignment. The sequence can be typed in or pasted from a selection made in another window.
Duplicate sequence: Duplicates the currently selected sequence with prefix D_ in its name.
Complement sequence: Creates a new sequence equal to the complementary strand of the currently selected sequence with prefix C_ in its name.
Reverse sequence: Creates a new sequence by reading 3' -> 5' the currently selected sequence and named with prefix R_
Exchange Us and Ts: Exchange bases Us and Ts in all currently selected sequences.
Dot plot: Performs a dot plot analysis of the two selected sequences.
Consensus sequence: Computes the consensus of all currently selected sequences. At any site, the consensus residue is the most frequent one if its frequency is above a threshold value. This threshold (60 % by default) can be changed through item "Consensus options> Edit threshold" of menu Props. Below threshold, N or X is used.
Del gap-only sites: Deletes all gap-only sites from the alignment.
Set genetic code: Allows to specify the genetic code used to translate to protein the selected sequence(s). Active only with nucleotide alignments. Genetic codes are saved if the mase or NEXUS file formats are used.

Align Menu

Align all
Align selected sequences:
Runs the chosen alignment program on all or on selected sequences. Alignment program is chosen with Alignment options of menu Align. With MSWindows and Unix, the chosen alignment program is searched in the directory of the seaview program and in directories of your PATH.
Align selected sites: Runs the chosen alignment program on the block of selected sites and the set of selected sequences. A window will ask for choosing the reference sequence: gaps present before alignment in the chosen sequence will be preserved in the new alignment.
Profile alignment: Align selected sequences against a profile, that is, a group of pre-aligned sequences.
Possible operations for making a profile alignment:

  1. select members of the profile group;
  2. do 'Create group' of menu Species;
  3. select sequences you want to align against the profile group;
  4. do 'Profile alignment' of menu Align;
  5. choose the profile group in the dialog menu;
  6. choose alignment algorithm;
  7. if using clustalw2, choose between "each sequence to profile" and "profile to profile" (with "profile to profile", selected sequences are expected to be pre-aligned to each other). With clustalw2, option Quicktree is possible.
  8. Uncheck "Propagate gaps to sites" if you don't want gaps created in the profile group by the profile alignment to be propagated to all your site selections (menu "Sites").

De-align selection: Remove all gaps from selected sequences.
Alignment options:
Props Menu

Fontsize: 8, 10, ..., 36: Sets the font size used to display sequences.
View as proteins: When ON, DNA sequences are displayed as translated to protein sequences. This allows to align them, and to go back to the DNA level by unselecting this item. Items Save/Save as of menu File and sequence edition are impossible when ON.

Allow seq. editing: When ON, residues can be deleted/inserted. When OFF (normally), only gaps can be deleted/inserted.
by Reference: To display the alignment by reference to a particular sequence: residues identical to that of the ref. seq. are displayed as dots. Possible only when one sequence, the reference, is selected. Alignment edition is impossible while in the reference mode. When used, item "Prepare pdf" of menu "File" produces an output by reference. Combination ctrl/cmd+R is a shortcut for calling/exiting this mode.
DNA keys: Allows to use keys "hjkl" to enter DNA sequences. "Allow seq. edition" should be ON for this item to be usable. Choose in the submenu what bases will be mapped to these keys: hjkl => GATC, hjkl => TCGA, hjkl => ACGT. Also, the space bar will be mapped to base N.
Consensus options: Allows to set the percent of identical residues needed to define a residue when building a consensus sequence. Sites where this fraction is not reached are filled with N or X (or, for DNA, with nucleotide ambiguity symbols if "Use IUPAC symbols" is on). If "allow gaps" is on, gaps are treated as another character state to compute consensus.
IUPAC nucleotide ambiguity symbols

Allow lowercase: If set, lowercase residues will be apparent. If not set, lowercase residues in sequence files display as uppercase.
Customize: To change, possibly permanently, various display settings. See Miscellaneous options and Sequence coloring help items. Apply: applies changes in current program session. Set changes permanent: applies changes in current and future program sessions. Close: ignores changes.
Sites Menu

Site sets allow to specify parts of a multiple alignment to be retained for further analyses (e.g., those parts of the alignment taken as reliably aligned). Retained sites are depicted as series of Xs on a special line at bottom of the alignment panel. Mouse clicks and drags on this line allow to construct/alter the set (see Mouse use on the site line).

Several sets of sites can be created and stored with the alignment if the Mase or NEXUS formats of alignment files are used. Each set has a name chosen by the user. One set of sites at most can be displayed at any time through this menu.

Item Save selection of menu "File" allows to save in an alignment file only those sites of the alignment pertaining to the currently displayed site set.

Create set: creates and names a new site set and displays it at bottom of alignment. A custom site set or, for nucleotide sequences, one of four codon position masks, or the set of all variable sites, can be created. Custom site sets are initially defined to contain all alignment sites, and should be named by the user. Codon position masks and the variable sites set are precomputed and named by the program. They are better used once alignment operations are completed.
Duplicate set: duplicates the current set of sites under a new name
Hide set: hides (but remembers) the current set of sites
Delete set: removes the currently displayed set of sites from list of known sets
name: shows the site line of name name. It can have been read in together with the alignment data, or previously created by "Create set".

Species Menu

Species sets can be created and stored with the alignment if the Mase or NEXUS formats of alignment files are used.

To select one or several species, click or drag on their names; they will appear in black background.

To memorize the current set of selected species, choose "Create set" from this menu. The program will ask for a name for this set.

Delete set: deletes (just from memory) the current set of species.
name: displays with black background the set of species memorized under that name.

Footers Menu

Comment lines can be created and displayed at bottom of the screen. These lines can contain any text and the program will maintain the vertical alignment between this text and sequences. This text can be saved using the mase or NEXUS file formats only.

To edit this text, click on the line name, position the cursor, and type text.
Click again on the line name to stop editing this text.

Show / Hide footers: To show / hide all footer lines
Create footer: To create a new footer line
Delete footer: To delete the currently selected footer line


Type a string in box at right and strike <return> key or push button to position the cursor in the next occurence of this string from its current place.

Push button to position the cursor at next occurence of the current search string.

Sequence gaps are ignored by the search procedure.


Moves the cursor to desired position or sequence:

Trees Menu

This menu allows to compute, draw, save, and import DNA or protein phylogenetic trees.
Protein-coding DNA sequences displayed as protein sequences (item "View as proteins" of menu Props) are treated as protein sequences.
All tree computations apply to selected sequences (or all if none) and selected sites (or complete alignment if none).
All trees, sequence, and site selections can be saved together with the alignment data in either the mase or Nexus formats.

Computes parsimony trees using PHYLIP's v3.52 dnapars or protpars programs and returns the strict consensus of all equally parsimonious trees found, without branch lengths.
Randomize seq. order: to repeat search for shortest trees with randomized sequence order.
Ignore all gap sites: if on, all gap-containing sites are excluded from analysis.
Gaps as unknown states: if on, gap-containing sites are coded as unknown states so don't introduce parsimony steps; if off, they are treated as an additional character state. The interface forbids the meaningless configuration that would ignore gaps and treat them as unknown states.
Equally best trees retained: maximum number of equally best trees retained in search.
Bootstrap: performs bootstrap evaluation of clade statistical support (can be interrupted).
User tree: computes the number of steps of a user-given tree taken from those in the trees menu. Such trees can have been previously computed or imported from external source.

Distance methods:
Computes NJ or BioNJ trees on a variety of pairwise phylogenetic distances.
NJ/BioNJ: to select the tree-building algorithm
Save to file: does not compute any tree but saves sequence pairwise distances to a local file.
Distance: select one among a variety of evolutionary distances: J-C: Jukes & Cantor (1969); K2P: Kimura (1980) JME 16:111; HKY: Rhzetsky & Nei (1995) MBE 12:131; LogDet: Lake (1994) PNAS 91:1455; Lockhart et al. (1994) MBE 11:605; Ka/Ks: Li (1993) JME 36:96.
ignore all gap sites: if on, all gap-containing sites are excluded from analysis; if off, not all sequence pairs use the same set of sites for computation of distances.
Bootstrap: performs bootstrap evaluation of clade statistical support (can be interrupted).
User tree: computes least squares branch lengths for selected user tree topology.

Computes trees using PhyML v3.0.1 as an external program.
If needed, PhyML can be downloaded from
Under Unix, file $HOME/.seaviewrc may contain the name of the PhyML executable used by seaview.
Please quote: Guindon S, Gascuel O. (2003) "A simple, fast, and accurate algorithm to estimate large phylogenies by maximum likelihood." Systematic Biology 52(5):696-704.
Model: select one among a variety of evolutionary models.
Branch support: can be omitted (None) or estimated either by the approximate likelihood ratio test approach (aLRT) or by bootstrap.
Ts/Tv ratio: (applies to some nucleotide models only) optimize or fix a priori this ratio.
Invariable sites: ignore (None), optimize, or set to an a priori value (Fixed) the fraction of invariable sites.
Across site rate variation: ignore (None), optimize, or set to an a priori value (Fixed) the alpha parameter of the gamma distribution of rates across sites. If not ignored, the # of rate categories must also be set.
Tree searching operations: NNI (nearest-neighbor interchange), SPR (subtree pruning and regrafting) and 'best of NNI & SPR' are options improving the search for the most likely tree but requiring increasing computation time.
Starting tree: controls the tree used to start tree-space search; can be BioNJ, a user-given tree from the trees menu, or a number of random trees (possible only with SPR). Turn off "Optimize tree topology" to compute the likelihood of a user-given tree.

Import tree: to import an external, Newick-formatted tree.

New tree window: opens a new, empty tree window.

Tree windows
Plots/saves/prints/copies phylogenetic trees that can be rooted or unrooted, with or without branch lengths, binary or multibranched, with or without internal bootstrap support values.

File menu

Save to Trees menu: to save in menu Trees of alignment window a previously computed tree.
Remove from Trees menu: removes a tree from menu Trees of alignment window.
Save rooted (unrooted) (sub)tree: saves displayed tree or subtree to a local file as rooted or unrooted form.
Print: (Mac OS and MSWindows only) prints displayed tree (see also 'Page count' below).
Save as PDF/PostScript: saves displayed tree to PDF (or PostScript) local file (see Page Count).
Save as SVG: saves displayed (sub)tree to a scalable vector graphics (SVG) local file suitable to be edited using appropriate programs (e.g., Inkscape).
A4 - Letter: controls the page format for PDF/PostScript operations.
Page count>#: controls the # of pages used for print/PDF/PostScript operations.
Reorder following tree: reorders sequences of alignment window as in displayed tree.
Select in alignment: selects in alignment window all members of subtree (active when only a subtree is plotted).
Open tree or alignement: opens a new tree (Newick format) or alignment file (any format).
New window: opens a new, empty tree window where a Newick-formatted tree can be pasted from clipboard.
Close window: closes the displayed tree that gets lost unless it had been saved to Trees menu.

Edit menu

Copy: (Mac OS and MSWindows only) copies tree plot to clipboard for pasting to external programs.
Paste tree: to paste a Newick-formatted tree contained in the clipboard (only if window is empty).
Find: finds sequence names in tree that contain a user-given string, and red-colors them in tree display (case insensitive).
Again: repeats 'Find' operation with same matching rules.
Edit tree header: to change the tree's brief descriptive header line.
Bootstrap threshold: only bootstrap values above given threshold become displayed.
Root at tree center: roots the tree at its point most equidistant to all leaves (when branch lengths exist).
Get or Set window size: to control the size of the current tree window.
Edit tree shape: to alter tree shape by moving or deleting sequence groups. A new window displays the tree without branch lengths. Clicking on a square selects a sequence group that appears in red. It can be moved to another branch of tree by clicking on another square, or deleted ("Delete group" button). "Select group" button allows to select another group for further move or delete operations. Complete edits by pressing "End edit" button, and, possibly, "File/Save to Trees menu".

Font menu: to control font, style and size of all text in tree display.

Br lengths: toggles display of branch length values next to each branch (very small values are not displayed).
Bootstrap: toggles display of bootstrap (or aLRT) support value next to each branch.

squared/circular/cladogram: toggles display between squared plot convenient for rooted trees, circular plot convenient for unrooted trees, and cladogram which displays trees with all branch lengths a multiple of a unit length and all leaves aligned at right. Cladogram is not available for branch length-free trees because it is equivalent to the squared display for them.

Full: normal, full tree display.
Swap: to swap branches around a node. Click on relevant square that appears.
Re-root: to set tree outgroup. Click on relevant square that appears.
Subtree: to limit display to a subtree. Click on relevant square that appears.
Subtree up: when a subtree is being displayed, adds one more node towards tree root to display.

Zoom: vertical zoom for tree display; one or two scrollers appear. The tree can be moved by the scrollers, the mouse wheel, or by clicking on and dragging the plot.

Dot Plot
Performs a "dot plot" analysis of two sequences

Enter desired values for the window size and # of matches/window, and click on button "Compute", the dot plot will appear.

Click in the dot plot, the corresponding sequence regions appear in the alignment panel above the dot plot. Use "Magnify" to take a close look.
Click on arrows at left to move the hit point by one residue in either of six directions.
Move the slider below the alignment panel to control the number of displayedresidues.

Fit to window, Reduce, Magnify: perform zoom in and out operations
Write PDF/ps: saves the dot plot to a PDF or PostScript file.
Close: closes the dot plot window

To perform a dot plot-guided alignment

Click on a diagonal representing two sequence parts to be aligned, then click on button "align". Repeat this for each sequence parts you want to be aligned to each other.
To transfer into the multiple alignment the result of these operations, click on button "Record alignment".
Most often, one of the two compared sequences is already aligned to other sequences of the multiple alignment, while the other one is not. Choose which of the two sequences is already aligned by clicking on the arrow next to "Ref. sequence".
Mase file format
Mase files follow the following format:

Zero or more header lines each beginning with ;;
Next, for each sequence in the alignment:
One or more comment lines each beginning with ;
Sequence name alone on a line (may be long and may contain spaces)
Sequence data in free form, possibly with numbers and spaces ignored while reading the file. Dashes denote gaps.

Header lines may contain any text and also contain descriptions of trees, site sets and species groups when such data have been defined.

Trees are as in this example:

;;$ BioNJ tree
;;[BioNJ 658 sites J-C](((boli_haplo_03:0.00146,boli_haplo_06:0.00159):0.00159,bol

Site sets are written as in this example:

;;# of segments=10  mychoice
;; 14,74 221,256 416,449 990,1148 1363,1384 1474,1483 1556,1668 2034,2062
;; 2114,2139 2756,2859
where "mychoice" is the name of the set of sites and where the series of pairs of numbers lists the endpoints of successive block of sites.

Species groups are written as in this example:

;;@ of species = 4 distant outgroup
;; 2, 3, 4, 5
where "distant outgroup" is the name of the species group and where the series of numbers lists the ranks of sequences members of the species group.
Program arguments
Under MSWindows and Unix, seaview can be run by command:
seaview [options] [filename]

where options may be
         [format_name, either  mase, clustal, phylip, msf, nexus or fasta sets 
          the initial file format for saving operations and for opening the file
          given on command line; default is mase]
         [sequences will be displayed faster but less smoothly]
         [residues will appear as black letters on a colored background]
-fontsize n
         [sets to integer n the initial fontsize of the alignment panel]

and filename 
is an optional alignment file to be loaded. 

Use item "Customize" of menu Props to further customize the program.

Sequence Coloring
The item "Customize" of menu Props allows to control colors.

A,C,G,T/U buttons show the colors that are in use for the corresponding nucleotide.
Click on a button to open a color chooser and select the desired color (OK will accept the new choice; reset will use the starting shade).
"reset" will use default colors.
"Apply" or "Set changes permanent" will apply new shades to current alignment.

aa coloring scheme: by default, amino acids are split in 8 families each displayed in a different color. These families can be customized, up to a maximum of 10. Also, an alternative coloring scheme can be defined, and seaview will allow to switch between the first and the alternative coloring schemes.

catalog of amino acid colors: colors used for each amino acid family. Click on any to control the desired shade, as explained above. White is used for gaps and for unlisted residues.

Example: with the default coloring scheme, groups of amino acids KR and AFILMVW are displayed with the first and second catalog colors starting from left, respectively.

Click "reset" to use default amino acid families and color catalog. "Apply" or "Set changes permanent" to apply new shades to current alignment.

Click on "Change" button. A window with a series of color cells appear. The 21 sets of synonymous codons and of stop codons can be colored with any of these colors. Click on a color cell and type a one-letter amino acid (or * to refer to stop codons) to reaffect a codon set to a new color. Repeat these operations as many times as necessary. Click on "OK" button when color re-assignments are complete.
Back to "Customization" window, "Apply" applies color re-assignments to this session's windows, "Set changes permanent" applies them to future seaview sessions as well.

Miscellaneous options
The item "Customize" of menu Props allows to set these options: