project_files

Project files: .qetz and .qet

QElectroTech saves a project in one of two kinds of file:

	.qetz — zipped project	.qet — project
What it is	a zip archive: one file per folio, the symbols, title blocks and pictures as files, and the engineering data in an SQLite database	one XML file holding everything
Default for saving	yes, since PR #1472 (merged 14 October 2026)	it was, before that
Opens in	QElectroTech 0.200.1 development builds since 14 October 2026	every version
Size	small: compressed, each picture stored once as an image file	large: pictures are stored as base64 text

Both hold the same project. Opening a .qetz and saving it as .qet gives the same file a plain .qet save gives, and older .qet files keep opening as they always did.

The format was added as a choice in PR #1462 and made the default in #1472; the discussion behind it is #1440.

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1. What Save does now

You…	QElectroTech…
save a new project	asks for a name in Save as, with the file type Zipped project QElectroTech (*.qetz) selected
save a project opened from a .qetz	writes the .qetz again
save a project opened from a .qet	writes name.qetz beside name.qet and leaves the .qet as it was. The project is then the .qetz
choose File → Save as	lets you pick either file type
choose File → Save a copy for an older QElectroTech	writes a .qet copy; the project keeps its own file

The first time you save a project opened from a .qet, a message titled Save as a zipped project says what is happening:

This project was opened from name.qet. It is saved as name.qetz, beside it, in the zipped project format; name.qet stays as it is.

To write a file for a version of QElectroTech that cannot open name.qetz, use File > Save a copy for an older QElectroTech.

If name.qetz already exists there, the same message asks Replace it? first; Cancel saves nothing.

The automatic backup (Automatic backup of projects in Settings → Configure QElectroTech → General) saves the same way, without the message: a project opened from a .qet gets its .qetz beside it.

A read-only folder

If the .qetz cannot be written beside the .qet — the folder is read-only, for example — the save fails with Cannot save and the file name, and the project stays the .qet it was opened from. Use Save as to save it somewhere else. Development builds from 14 October 2026, before PR #1483, showed only "Permission denied" and then named a .qetz that did not exist.

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2. Keeping .qet

There is no setting that makes .qet the default again. Two ways to get a .qet:

• File → Save as, file type Project QElectroTech (*.qet). The project is then that .qet, and later saves write it.
• File → Save a copy for an older QElectroTech. It writes a .qet and leaves the project on its own file, so later saves still write the .qetz. Use it to hand a project to someone on QElectroTech 0.200.0 or older.

Typing a name ending in .qetz in Save as saves a .qetz whichever file type is selected.

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3. Opening

File → Open lists both under QElectroTech project (*.qet *.qetz), and a .qetz opens like any project: from the command line, the recent files list, or a double-click once file types are registered (§7).

A .qetz from a later version. The file says which format it is and the oldest format allowed to read it. If a later QElectroTech wrote it but allows this one to read it, the project opens read-only, with the message This project was saved by a later version of QElectroTech. It is opened read-only, so that saving it cannot lose what this version does not know. Use Save As to keep a copy in this version's format. If it does not allow it, the file is refused with a message saying it was made by a later QElectroTech.

A damaged or hand-edited .qetz is refused with a message saying what is wrong: an unsafe or repeated name in the zip, a database whose rows do not match the folio files, and so on. Nothing in the file is run.

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4. What is inside

A .qetz is an ordinary zip; any unzip tool opens it.

unzip -l project.qetz

Entry	Holds
mimetype	application/x-qet-project+zip
manifest.xml	the format number, the oldest format allowed to read the file, and the QElectroTech that wrote it
project.xml	the project's own settings (defaults for new folios, numbering, cables) and the list of its folios, symbols and title blocks, each pointing to its file
project.sqlite	the engineering data, see below
folios/<uuid>.xml	one file per folio: what is drawn on it and where
elements/…	the project's copy of each symbol it uses, as .elmt files
titleblocks/<name>.titleblock	the project's title block templates
images/<sha256>.png	each picture once, as an image file

Each fact is kept once. The database holds what things are; the folio files hold where they are drawn:

	in project.sqlite	in the folio file
Symbol	its information (label, comment, manufacturer…), label prefix, cross-reference links	which symbol it is, position, rotation
Wire	its two ends, number, function, voltage, colour, section	its path, where its number is drawn
Folio	title block fields and custom variables	everything drawn on it
Terminal strip	its terminals, their order and bridges	the strip as drawn

What QElectroTech works out again when it opens a folio — a symbol text that only shows the symbol's information, a wire's description of its ends — is not stored at all.

Saving twice gives the same bytes. Every entry is dated 1 January 1980, not with the save time, so a project saved again without changes is byte-for-byte the same file (PR #1467). Development builds from before that wrote dates that unzip tools showed as 1979 or 1901.

The full format — every table and column, how rows are keyed, the version rules and what reading checks — is sources/container/QETZ-FORMAT.md in the source tree.

The tables in project.sqlite

Table	One row per
meta	setting of the file, including format
project_property	project-wide variable
folio	folio, in folio order (pos from 1), with its title block fields as columns
folio_property	custom title block variable of a folio
element	symbol placed on a folio: its label prefix and frozen-label flag
element_info	piece of symbol information (name, value, show)
link	cross-reference link of a symbol
conductor	wire: its two ends, number, formula, function, voltage, colour, section, cable
terminal_strip, strip_terminal, strip_bridge, strip_bridge_terminal	terminal strip, terminal, bridge, bridged terminal

Every row is keyed by its item's uuid — a folio, symbol or wire keeps its row when folios are reordered (PR #1473). True/false values are stored as 0/1. The format number is also in PRAGMA user_version.

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5. Reading the database yourself

Unzip project.sqlite and open it with any SQLite tool — the sqlite3 command line, DB Browser for SQLite, Python, LibreOffice Base:

unzip -o project.qetz project.sqlite -d extracted
sqlite3 extracted/project.sqlite ".tables"
sqlite3 extracted/project.sqlite \
  "SELECT e.uuid, i.value FROM element e
     JOIN element_info i ON i.element_uuid = e.uuid
    WHERE i.name = 'label' ORDER BY i.value;"

Without unzipping, from Python:

import sqlite3, tempfile, zipfile

with tempfile.TemporaryDirectory() as tmp:
    zipfile.ZipFile("project.qetz").extract("project.sqlite", tmp)
    db = sqlite3.connect(f"{tmp}/project.sqlite")
    for folio, title in db.execute("SELECT pos, title FROM folio ORDER BY pos"):
        print(folio, title)
    db.close()

Two things to know:

• Read, do not edit. QElectroTech checks that the database and the folio files agree when it opens the file, and refuses it if they do not. Change a project in QElectroTech, or with a script.
• This is not the database the parts list reads. The views behind parts lists, the wiring list and summary tables (element_nomenclature_view, wiring_list_view…) belong to the working database QElectroTech builds when a project opens; they are not in the file. See The project database.

Other tools that take a .qetz:

• The command line: the exports and --info take a .qetz as they take a .qet, and --resave writes a .qetz when the output name ends in .qetz, a .qet otherwise — a way to convert in either direction:

  qelectrotech --resave old.qet new.qetz
  qelectrotech --resave project.qetz for-older-versions.qet

  See CLI Reference.

• The MCP server reads and writes .qetz (it converts through QElectroTech, so the first read of a big one takes as long as a save).

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6. Opening big projects faster

Folios built when they are first shown

Building a folio — creating every symbol, wire and text on it — is most of the time a big project takes to open. Since PR #1468 (and by default since #1472), QElectroTech reads every folio's title block and data when a project opens, but builds a folio's drawing only when it is needed:

• opening shows the first folio and builds it;
• clicking a folio's tab builds that folio the first time, together with the symbols on other folios that its cross-references and folio reports point to;
• printing, exporting, and Search and replace build every folio first;
• numbering, the wiring list export, and changing a folio's title, author or revision work from the project database, without building folios.

This works for .qet and .qetz alike, but only for a file that gives every folio, symbol and wire its own uuid — anything saved by a recent version. An older file opens with every folio built, as before, and the log says why, for example:

Project opened with every folio built: a folio has no saved uuid

Saving it once with this version adds the uuids (PR #1471).

To build every folio on opening anyway — to compare, or if something looks wrong — start QElectroTech with the environment variable QET_EAGER_FOLIOS=1:

QET_EAGER_FOLIOS=1 qelectrotech project.qetz

The variable QET_LAZY_FOLIOS=1, which switched this on before #1472, no longer does anything.

What it gives

Measured in PR #1472 on a 136-folio project:

	.qet	.qetz
Open	23 s	3.5 s
File size	17 MB	2.2 MB

Saving a .qetz writes the folios you have not changed straight from the file without building them. The first save of a .qet as a .qetz builds every folio once.

Pictures

• In a .qetz, each picture is an image file handed straight to its folio (PR #1470): a project with 140 MB of pictures opened in 3.8 s instead of 11.8 s. A .qet with pictures also opens faster: each picture is decoded once instead of twice.
• The pictures of one folio are decoded at the same time, one per processor core (PR #1477). A folio with 22 photos opened in 12.5 s instead of 21.3 s. A folio with only one picture gains nothing.
• A project saved before project uuids were stored no longer copies the whole file twice in memory while opening (PR #1476).

See Pictures on a sheet for what pictures cost in the file.

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7. File type registration

System	How .qetz is registered
Windows, installer	the installer associates .qetz with QElectroTech, like .qet
Windows, portable archive	register_filetypes.bat registers .qetz too — see Windows without admin rights
Linux	MIME type application/x-qet-project+zip, in the shared MIME file and the AppStream data
macOS	declared in the application's Info.plist

Development builds from 13–14 October 2026 wrote the MIME type as application/x-qelectrotech-project+zip (PR #1483 renamed it); those files still open, and the Linux MIME file recognises both.

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8. Limits

• QElectroTech 0.200.0 and older cannot open a .qetz. Hand them a copy from File → Save a copy for an older QElectroTech.
• A .qetz is not one text file. To read or diff it by hand, unzip it: the folio files and project.xml are XML, the engineering data is in the database. For a single XML file, save a .qet.
• Do not edit the inside of a .qetz by hand. A database row with no item, or an item with no row, makes the file refused.
• The first save of a .qet as .qetz, printing, exporting and Search and replace still build every folio.

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See also

• The project database — the working database built when a project opens, and what reads it
• Project XML — the XML a .qet holds, and a .qetz holds in parts
• CLI Reference — --resave, exports, --info
• Pictures on a sheet
• FAQ