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CLI Mode

OrcaSlicer can run headless from the command line to load, transform, and slice models without opening the GUI. This is useful for automation, batch processing, and CI pipelines.

Invocation

orca-slicer [input files...] [options...]

Any argument that doesn't start with - is treated as an input file (model or project) to load, in the order given. Supported input formats are the same ones listed under Supported File Formats.

Use -- on its own to stop OrcaSlicer from parsing any further arguments as flags — everything after it is treated as a positional input file, even if it starts with a dash.

Flag Syntax

Boolean flags

Flags backed by a plain on/off setting (e.g. --info, --export-stl) don't need a value — including the flag alone enables it. An explicit =1 / =0 is also accepted to force it on or off. See Boolean for the full rules, including a space-separated --flag 0 gotcha that does not do what it looks like it does.

Value flags

Flags backed by a single value accept it either as a separate argument or with =:

--slice 0
--slice=0

Important

Every setting's key (as shown on its wiki page, e.g. layer_height) uses underscores. On the command line, OrcaSlicer always converts underscores to hyphens to build the flag name — so layer_height becomes --layer-height. This applies uniformly: all ~50 CLI-only options and every regular print, filament, and printer setting alike. Always write CLI flags with hyphens, never the raw underscore key.

Vector (multi-value) flags

Some settings hold one value per extruder, filament, or object (e.g. retraction_length[extruder_idx]). These take a comma-separated list, where position in the list = index (0-based):

--retraction-length=0.8,0.8,1.2,0.8

Two behaviors to know before using these:

  • Padding. If you supply fewer values than there are entries (extruders, filaments, etc.), the missing slots are filled by repeating the first value you gave — not each entry's own default. --retraction-length=1.2 on a 4-extruder printer becomes [1.2, 1.2, 1.2, 1.2]; --retraction-length=0.9,0.8,1.2 on 4 extruders becomes [0.9, 0.8, 1.2, 0.9] (index 3 silently gets 0.9, the first value, not its default).
  • Repetition appends, not overwrites. Passing the same vector flag more than once appends to the list instead of replacing it: --retraction-length=0.8 --retraction-length=1.2 results in [0.8, 1.2], not [1.2]. To fully replace a vector's contents, pass the whole list in a single flag occurrence.

Setting Overrides

Beyond the CLI-only options documented on this wiki (see Reference Pages below), --key=value accepts almost any print, filament, or printer/machine setting documented under Printer Settings, Material Settings, and Process Settings — the same settings shown in the GUI's Printer/Filament/Process tabs. Each option's page shows its key next to a [Variable]/[Variables] tag; convert underscores to hyphens to get the flag name, following the Flag Syntax rules above for booleans, values, and vectors.

A fixed set of 43 keys are never exposed on the CLI at all. If a --key=value override is rejected with Invalid option, check it against the list below before assuming it's a typo:

Preset identity & inheritance (used when hand-authoring .json profiles directly — see How to Create Profiles): preset_name, compatible_printers, compatible_printers_condition, compatible_prints, compatible_prints_condition, compatible_machine_expression_group, compatible_process_expression_group, different_settings_to_system, print_compatible_printers, default_filament_profile, default_print_profile, filament_ids, filament_vendor, inherits, inherits_group, host_type, printer_model, printer_variant, material_vendor, default_sla_material_profile, sla_material_settings_id, default_sla_print_profile, sla_print_settings_id

Print host / network connection (credentials and connection details for sending directly to a networked printer): bbl_use_printhost, use_3mf, printer_agent, print_host, print_host_webui, printhost_apikey, flashforge_serial_number, printhost_port, printhost_cafile, printhost_user, printhost_password, printhost_ssl_ignore_revoke, printhost_authorization_type

Internal extruder/variant indexing (bookkeeping OrcaSlicer maintains internally to match extruders across printer/print/filament configs): extruder_variant_list, printer_extruder_id, printer_extruder_variant, print_extruder_id, print_extruder_variant, filament_extruder_variant, filament_self_index

Reference Pages

CLI-only options are grouped the same way they're grouped in the source (CLIActionsConfigDef, CLITransformConfigDef, CLIMiscConfigDef):

  • Actions — what to do with the loaded model(s): export, slice, inspect.
  • Transform — arrange, orient, rotate, scale, and other geometry changes applied before slicing.
  • Misc — loading settings/filaments, output locations, logging, and metadata.

Example

orca-slicer model.3mf --load-settings "process.json;printer.json" --load-filaments filament.json --arrange 1 --slice 0 --export-3mf output.3mf

Loads model.3mf, applies the given process/printer/filament settings, auto-arranges the plate(s), slices every plate, and exports the result as a 3MF.