How to Open PLT File: Free HPGL Viewer for Windows, Mac & Phone

What is a PLT file?

A PLT file is a plot file: a list of instructions that tells a pen plotter, large-format printer or cutting plotter where to move and draw. Almost all of them are written in HP-GL (Hewlett-Packard Graphics Language), a plain-text language of two-letter commands that Hewlett-Packard introduced with its HP 9872 plotter in 1977 and that became a de facto standard for plotters. Its successor, HP-GL/2, added line widths and a more compact binary-style encoding.

PLT files are usually output, not working drawings. You get one when someone uses Plot to file in AutoCAD, exports "PLT - HPGL Plotter File" from CorelDRAW, saves a design for a vinyl cutter or sign plotter, or exports pattern pieces for a garment plotter. That's why a PLT has no layers, fills or real colors: it only knows lines, pen numbers and positions measured in plotter units of 0.025 mm.

How to open a PLT file (quick answer)

Short answer: you don't need AutoCAD. To open PLT files for viewing, printing or converting:

1. Drop the file into the viewer above. It runs in any modern browser on Windows, Mac, Linux, iPhone, iPad or Android.
2. Read the verdict. It says whether the file is HP-GL, HP-GL/2, a PCL-wrapped printer plot, PostScript, a gnuplot script, Tecplot data or a GPS track.
3. Check the drawing and its size. Each pen gets its own color, and the Details tab gives the size in mm and inches plus the total cut/line length.
4. Save it. Download SVG to scale, edit or convert it further, or PNG to share it. To edit it in CAD, see AutoCAD or CorelDRAW.

Which kind of PLT file do you have?

Four quite different things share the .plt extension. Open the file in a text editor (or the Raw data tab of the viewer) and the first line usually gives it away:

The gnuplot installer for Windows associates the .gp, .gpl and .plt extensions with wgnuplot, which is why double-clicking a plotter file sometimes opens gnuplot with a pile of errors. Tecplot calls its traditional binary format "PLT" and describes it as significantly more efficient than its plain-text ASCII format.

Inside an HPGL file: commands and units

An HP-GL file is readable text. Each command is two letters followed by numbers, ending in a semicolon. Coordinates are in plotter units: 40 per millimeter, 1,016 per inch (one unit = 0.025 mm), so PD4000,0 draws a line 100 mm long.

Two consequences matter when you open PLT files. First, there are no colors, only pen numbers: CorelDRAW's documentation notes that the format "does not contain color information", so every viewer picks its own colors (this one uses the HP-GL/2 default palette unless the file defines pen colors). Second, there is no page size in classic HP-GL, which is why some programs place the drawing off the page or at the wrong scale.

Files plotted to disk from Windows printer drivers often wrap HP-GL/2 inside PCL printer commands: an escape sequence such as ESC%-12345X with @PJL job lines, then ESC%…B to switch into HP-GL/2. Many simple importers stop at the first escape character. The viewer above skips the PCL parts and draws only the vectors.

Open PLT files on Windows 11 and 10

Windows has no built-in PLT viewer, so double-clicking does nothing useful (or launches gnuplot if it's installed). The quickest way to open PLT files on Windows without installing anything is the browser; for editing you need a graphics or CAD program. Your options:

• Open PLT file online (free): Edge or Chrome plus the viewer above. Good for checking a drawing, its size and its pens, and for exporting SVG/PNG.
• CorelDRAW (or Corel PHOTO-PAINT): File > Import, set the file type to PLT - HPGL Plotter File (*.plt; *.hgl), then pick colors and widths for each pen in the HPGL options dialog. Corel supports HP-GL versions 1 and 2, "although some features of version 2 are not supported".
• ViewCompanion (Software Companions, paid, 30-day evaluation): views and prints PLT files in HPGL, HPGL/2, KIPGL, HP-RTL and CalComp languages and converts them to PDF, TIFF, DWF, DXF, PNG and more. It's the usual pick for print shops and engineering offices that handle many plot files.
• AutoCAD with Express Tools: the PLT2DWG command, with limits explained below.

How to open a PLT file in AutoCAD (PLT2DWG and its limits)

AutoCAD can't open a PLT with File > Open, and a PLT can't be "un-plotted" back into the original DWG with its layers, blocks and dimensions. What you can do:

1. Classic HP-GL files: type PLT2DWG (part of the AutoCAD Express Tools) and choose the file. It imports the plot as lines, which you can then edit or save as DWG or DXF.
2. HP-GL/2 files (what modern AutoCAD and DesignJet drivers produce) are rejected with "The selected PLT file is not in the proper HPGL format." In a 2025 Autodesk forum case about AutoCAD 2024 plot files, the fix was to replot with a driver that writes true HPGL or to use a third-party converter.
3. Any PLT: open it in the viewer above, download the SVG, convert it to PDF (how) and bring it in with AutoCAD's PDFIMPORT command, which turns vector PDF content into editable geometry.

If you're the one who made the PLT, re-plot from the original DWG instead. Autodesk's help notes that you must use the plotter configuration for the actual output device "to produce a valid PLT file"; for sharing with people, plot to PDF with the DWG To PDF driver (see our DWG guide).

Open PLT files on Mac, iPhone, iPad, Android and Linux

Desktop PLT viewers are mostly Windows programs, so to open PLT files on other devices the browser is the simplest route:

• Mac: open the file in Safari or Chrome with the viewer above, then save the SVG. Inkscape (free) can open that SVG and also has its own HPGL import for .hpgl files, but that importer is aimed at files Inkscape wrote and doesn't handle commands such as CI circles, so use the SVG route for files from other programs.
• iPhone and iPad: in Safari, tap the drop area, choose the file from the Files app and view it. Downloaded PNGs can be saved to Photos.
• Android: same in Chrome: tap the drop area and pick the file from Downloads or Drive.
• Linux: the browser viewer, or the old GNU command-line converter hp2xx, which turns HP-GL into formats such as EPS and works as a previewer (its project page was last updated in 2000, and it predates most HP-GL/2 features).

If the .plt is an OziExplorer GPS track instead, GPXSee is free and open source for Windows, macOS, Linux and Android and lists OziExplorer PLT among its supported formats.

Convert PLT to PDF, SVG, DXF or PNG

The free route for any HP-GL plot file is PLT → SVG with the viewer on this page, then SVG to whatever you need. Lines stay vector, so nothing gets blurry:

The SVG keeps the drawing's real size (its width and height are written in millimeters), so programs that read SVG dimensions, such as Inkscape, open it at its real-world scale. When printing to PDF from a browser, choose the paper size and scaling in the print dialog.

PLT files for plotters and vinyl cutters

For a cutting plotter, each PD stroke is a cut, each pen number can be a different tool or pass, and the drawing size is the material you need. The viewer's Details tab gives exactly that: size in mm/inches, pen-down length (total length of lines or cuts) and pen-up travel. Tick "Show pen-up moves" to see the path the head takes between cuts.

Sending a PLT straight to a plotter

A PLT made for a particular plotter already contains its commands, so it goes to the device unchanged. Autodesk's help describes doing this with a batch file built on the Windows copy command. In Command Prompt:

Microsoft's documentation explains that /b copies the data in binary mode, so control characters reach the device intact. Many vinyl cutters are driven through their own cutting software instead; check that it lists PLT or HPGL among its import formats.

Making a PLT for a cutter from Inkscape

Inkscape users on its forum describe the working method: convert text and objects to paths, set the stroke and remove the fill, then File > Save As > HP Graphics Language File (*.hpgl), and rename the result from .hpgl to .plt if your cutter software expects that extension. Open PLT files in the viewer above before you cut, to check the size and the path.

Is a PLT file safe? Can I delete it?

Yes, a PLT file is safe to open. HP-GL is a description of pen movements, not a program; viewing it only draws lines. The real risk is practical: a plot with the wrong scale or a stray pen-up move wastes a large sheet or a roll of vinyl, which is why it's worth previewing first.

You can delete PLT files once the job is plotted. They're copies of output, and the original drawing (DWG, CDR, SVG) is what you'd edit and plot again. Keep them only if they are the only version you have, for example plots received from a client or an archive of old drawings.

Can't open a PLT file? Common problems and fixes

When a program refuses to open PLT files, the cause is almost always one of these.

"Not in the proper HPGL format" in AutoCAD

The file is HP-GL/2, often inside a PCL wrapper, and PLT2DWG only accepts classic HP-GL. Use the SVG or PDF route in the AutoCAD section.

The drawing is blank, tiny or off the page

HP-GL has no page size, so importers guess. The file may also use SC scaling or draw only with pen 0. The viewer above fits whatever is drawn to the screen and reports its true size; if it says nothing is drawn, the file has no pen-down moves.

Double-clicking opens gnuplot or shows errors

gnuplot's Windows installer claims the .plt extension. Right-click the file > Open with > choose another app, or just use the browser viewer.

The file opens as garbage text

It may be a Tecplot binary file, a raster plot (PCL/HP RTL) or PostScript. The viewer identifies all of these and tells you the right program.

Colors or line widths look wrong

That's normal: PLT files store pen numbers, and the color or width is chosen by whoever plots it. In CorelDRAW you set them in the import dialog; in the downloaded SVG you can recolor each pen in any vector editor.

Text looks different from the original

LB labels are drawn by the plotter's own font, so every viewer approximates them. Many CAD programs avoid this by plotting text as lines, in which case it looks exactly right.

Related file extensions

Sources and technical references

• HP-GL — Wikipedia — history (HP 9872, 1977), HP-GL/2 line widths, 25 µm plotter units.
• HP printer languages reference (PCL 5 / HP-GL/2) — one plotter unit = 0.025 mm, 1016 per inch; ESC%#B to enter HP-GL/2; PE polyline encoded.
• IANA media type application/vnd.hp-HPGL — registered MIME type.
• HPGL Plotter File (PLT) — CorelDRAW Help — versions 1 and 2, 1,016 units per inch, no color information.
• To import an HPGL Plotter file — Corel PHOTO-PAINT Help — File > Import and the PLT file type.
• To Work With Plot Files — Autodesk help — Plot to file, valid PLT files, sending them with a batch file.
• Can't open PLT file — Autodesk Community (2025) — PLT2DWG rejects HP-GL/2; PDFIMPORT and converters as workarounds.
• PLT2DWG command (Express Tools) — Bricsys help — imports HPGL plot files into a drawing.
• Software Companions (ViewCompanion) — HPGL, HPGL/2, KIPGL, HP-RTL, CalComp support and conversions; 30-day evaluation.
• PLT file export / save as / open — Inkscape forum — saving HPGL for cutters; PLT import removed with UniConvertor.
• Rewrite HP-GL import — Inkscape extensions — existing importer lacks CI circle, arc and polygon commands.
• DXF save-as options — Inkscape forum — AutoCAD DXF R12 and R14 output.
• hp2xx — GNU Project — HP-GL converter and previewer.
• gnuplot README-Windows — .gp, .gpl and .plt associated with wgnuplot.
• Tecplot data file types: DAT, PLT, SZPLT — Tecplot — PLT binary format.
• OziExplorer file formats — track file (.plt) layout.
• GPXSee — free viewer that opens OziExplorer PLT tracks.
• copy command — Microsoft Learn — /b binary copy to devices.

Frequently asked questions