Save in MATLAB: Workspace, MAT Files and the save Command

MATLAB variables live in the workspace and disappear when the session ends unless you save them. This guide is for researchers and analysts who need to save MATLAB work to a file and load it back reliably: which route to use (the Save Workspace button or the save command), how to add to an existing file, and what to do when a variable is too large for the default format.

What saving in MATLAB is used for in research

Saving the workspace writes variables to a MAT-file, MATLAB’s own binary data format, so an analysis can be resumed, shared with a collaborator or archived with a project. Per MathWorks’ documentation, variables do not persist between sessions unless you save them; MATLAB Online is the stated exception. Saving is separate from saving code: scripts and functions are saved from the Editor, while save and Save Workspace store data. For the data-table case specifically, see working with tables in MATLAB.

Install or access (official source only)

MATLAB is distributed by MathWorks; obtain and activate it only through mathworks.com. Installation steps are covered in MATLAB installation. The commands below are taken from the MathWorks documentation for save and for saving, loading and deleting workspace variables, both read on 2026-11-07.

Step-by-step: save a workspace in MATLAB

How do you save a workspace in MATLAB?

Use the Home tab or the save command. Both write a MAT-file; the command form lets you script it.

Option A: the desktop

1. To save everything, go to the Home tab, open the Variable section and click Save Workspace.
2. To save only some variables, select them in the Workspace panel, right-click and choose Save Selection.
3. In the dialog, choose a file name and location. Choosing the MATLAB Script type writes the variables as a script; variables that cannot be written to a script are saved to a MAT-file with the same name.

Option B: the save command

1. Save all variables: save("june10") writes june10.mat in the current folder.
2. Save chosen variables: save("june10","A","B").
3. Check what was written: whos -file june10.mat lists the variables in the file (sizes shown are in-memory sizes).

Decision table: which save form to use

You want to	Use	Note from the documentation
Save everything once, by hand	Home > Variable > Save Workspace	Dialog also offers the MATLAB Script type
Save a few variables by hand	Select in Workspace panel, right-click > Save Selection	Saves only the selection
Save everything from code	save(filename)	Command form save filename also works
Save named variables	save(filename,variables)	Variable names given as strings
Add variables to an existing file	save(filename,variables,"-append")	Adds new variables to an existing file; for a Version 6 file also specify -v6
Store struct fields as separate variables	save(filename,"-struct","structName")	Saves the fields of a scalar structure as individual variables
Save a variable of 2 GB or more	save(filename,variables,"-v7.3")	v7.3 supports variables of 2 GB or more on 64-bit systems; v7, v6 and v4 are limited to 231 bytes per variable
Skip compression	save(filename,variables,"-nocompression")	Supported only for v7 and v7.3; v7+ files are compressed by default
Write plain text numbers	save(filename,variables,"-ascii")	8-digit precision; add -double for 17 digits

The default MAT-file version is v7, and you can change it in Settings under the MAT-file save format. The -ascii route writes text rather than a MAT-file, so it does not preserve variable names or types; use it only when another program needs plain numbers.

Output and how to read it

Load a saved file back

Load with load("durer") for every variable, or load("durer","X","map") for named variables. In the desktop you can double-click the MAT-file in the Files panel, drag it into the Workspace, or use Import Data to bring in a subset.

Two behaviours to plan for:

• Loaded variables overwrite variables of the same name already in the workspace.
• S = load("durer") returns the contents as a structure S, so nothing in the workspace is overwritten; read fields as S.X.

A simple round-trip check: save("check","A"), clear A, load("check"), then confirm A is back with whos. To work with only part of a very large variable without loading all of it, the documentation points to matfile.

Troubleshooting

• A variable is too large to save. Version 7 and earlier files cap each variable at 2³¹ bytes (2 GB). Save with -v7.3.
• Appending to an older file fails or behaves unexpectedly. -append adds variables to an existing file; for a Version 6 file specify -v6 as well.
• Loading overwrote my variables. That is the documented behaviour; load into a structure with S = load(...) or load only named variables.
• File size looks different from whos. whos -file reports in-memory sizes, and v7 or later MAT-files are compressed by default.
• Variables vanished after restarting MATLAB. They are not kept between sessions unless saved (MATLAB Online excepted).

Free alternatives (table)

If a collaborator has no MATLAB licence, these tools read or write MAT-files. Limits are from each project’s own documentation, read 2026-11-07.

Tool	Save	Limits stated in its documentation
SciPy (Python)	scipy.io.savemat(file_name, mdict) writes a dictionary of arrays to a .mat file	Default format='5' targets MATLAB 5 up to 7.2; compression is off unless do_compression=True; structure field names limited to 31 characters unless long_field_names=True (needs MATLAB 7.6 or later)
GNU Octave	save with -v7, -v6 or -v4 writes MATLAB-compatible files	Default format is Octave text, not MAT; saving v7.3 is not supported; load reads MATLAB v4, v6 and v7, with only limited -hdf5 support for v7.3 files

FAQ

How do you save a workspace in MATLAB?

On the Home tab, in the Variable section, click Save Workspace; or run save("filename") to write all variables to filename.mat. To save only some, select them in the Workspace panel and choose Save Selection, or list them: save("filename","A","B").

Is MATLAB autosave on for the workspace?

The documentation says variables are not retained between sessions unless you save them, with MATLAB Online as the exception. Treat the workspace as unsaved until you have written a MAT-file.

Is .m file for MATLAB?

Yes. .m is the extension of MATLAB code files (scripts and functions), which you save from the Editor. A .mat file holds data. The Save Workspace dialog can also write variables as a MATLAB Script, which produces a code file rather than a MAT-file.

Can I save MATLAB data as text?

Yes: save(filename,variables,"-ascii") writes 8-digit text, or 17 digits with -double, but names and types are not kept.

Sources (official docs)

• MathWorks, save, read 2026-11-07.
• MathWorks, Save, load and delete workspace variables, read 2026-11-07.
• SciPy, scipy.io.savemat, read 2026-11-07.
• GNU Octave, Simple File I/O, read 2026-11-07.

Related guides: printing from MATLAB, MATLAB graphing.