Plot Styles (CTB / STB)
The mapping from on-screen color or named style to printer lineweight, color, screening, and dithering at plot time.
Definition
AutoCAD supports two plot-style models: color-dependent (.ctb) and named (.stb). A CTB maps each of AutoCAD's 255 indexed colors (plus extra for true-color objects) to a plotted lineweight, screening percentage, and plotted color. An STB instead lets every entity carry a named plot style independent of color.
A drawing can use either model but not both; the choice is made by the template and convertible per drawing.
Why it matters
Plot styles are why an AutoCAD sheet that looks identical on screen can plot completely differently across two offices. Standardising CTBs (or moving to STBs and naming the styles by intent) is what makes prints look consistent.
Technical Deep Dive & Core Mechanics
In 2D vector engines like AutoCAD, Plot Styles (CTB / STB) directly influences the system's memory-mapped database structure. Rather than storing arbitrary pixel rasters, the DWG/DXF format describes each entity using grouped DXF codes (such as code 10 for coordinates, code 8 for layers, and code 100 for class markers). The virtual screen index utilizes highly optimized spatial indexing trees (like quad-trees or R-trees) to manage viewport pan and zoom sweeps efficiently.
Cross-Discipline Collaboration & Handoff
In global multi-office projects, Plot Styles (CTB / STB) is a high-frequency handoff node between diverse software packages. During cross-platform export (for example, exporting AutoCAD drawings to IFC for coordination in Navisworks or Solibri, or converting mechanical STEP files into BIM detail families):
Common pitfalls
- Mixing CTB-mode and STB-mode drawings in one sheet set — viewport plot-style overrides won't behave intuitively.
- Editing colors instead of plot styles, then wondering why a 'fix' didn't change the output.
- Sending out the DWG without the plot style — recipient plots with their own CTB.
This concept is a core structural element of the AutoCAD drafting and engineering environment developed by Autodesk. The original commercial CAD platform — still the lingua franca of DWG-based 2D documentation across AEC, mechanical, and infrastructure work.
Relevant AutoCAD FAQs
❓ Why does my plot look different at home than at the office?
Almost always plot-style mismatch. AutoCAD plot styles (.ctb or .stb) live separately from DWG and are searched in the configured Printer Support File Path. Either embed your styles in the drawing's plot-style folder, or include them in your project package alongside the DWG.
❓ How do I move a customised AutoCAD installation to a new computer?
Use Migrate Custom Settings (or the Reset Settings to Default option for a clean start) and export your profile (Options > Profiles > Export). Also copy your acad.pgp (command aliases), partial CUIs, LISP files, custom blocks, templates, plot styles, and printer .pc3 files. Re-import the profile and link the file locations on the new workstation.
❓ What is the difference between PURGE and AUDIT?
PURGE removes unused named objects (layers, blocks, linetypes, text styles, dimension styles) from the drawing. AUDIT scans the drawing for internal errors and offers to fix them. RECOVER opens a damaged drawing while running an audit. Run all three on inbound DWGs before treating them as the model of record.
⚡ Concept Self-Test
🎓 Recommended Practice Lessons
Step-by-step practical exercises and certification-aligned paths chosen by our editors to master this concept:
AutoCAD Professional Design & Engineering Specialization
The Complete AutoCAD 2026 Masterclass: From Beginner to Pro
Autodesk Certified Professional (ACP) - AutoCAD Exam Study Guide & Mock Practice
🌳 Semantic Crossroads & Navigation Pathways
Trunk-Branch-Leaf ModelCore glossary, interactive graph, and domain-wide concept index.
Parent design environments and platforms implementing this method natively.