PPTX fidelity

Check which presentation features you can edit, display, and preserve on save. Each row summarizes the main limits; linked guides explain usage. The approximation lists describe visible differences you can expect.

Feature matrix

The matrix reports editing, rendering, and round-trip support separately. A feature can display without editing controls, or survive save without displaying.

The slide show and the image and PDF exports show No for round trip. They write nothing to the .pptx, so a save has nothing of theirs to keep.

When a feature needs @pptx-editor.dev/pro or @pptx-editor.dev/pptx-to-pdf, its note says so. These packages use the EigenPal Pro License. Evaluation is permitted. Production use requires a commercial agreement.

Text and formatting

Paragraphs and text boxes

Bullets and numbering

Shapes, groups, and connectors

Fills and lines

Effects

Pictures

Tables

Charts, diagrams, media, and OLE

Slides, layouts, and notes

Themes, masters, and inheritance

Presenting

Comments and review

Collaboration and automation

Export and print

Round-trip contract

• The editor keeps every part of the package that it does not edit. Unknown elements stay in place and survive save.
• XML parts are written again in a normalized form. Binary parts, such as pictures, media, and embedded fonts, keep their exact bytes.
• Every edit goes through one document store. An edit that the editor cannot make is refused with a reason. It is never dropped without notice.
• A full round trip preserves the feature's edit through save and reopen without changing unrelated parts. The saved copy opens without a repair prompt.
• A preserved feature survives nearby edits or changes to its box, followed by save and reopen. The saved copy opens with no repair prompt.
• Full rendering means that every test presentation of the feature matches its reference PDF within the fidelity thresholds. The feature has no approximation of its own. The line model, glyph advances, and missing glyphs apply to all text.
• Macros, OLE objects, audio, and video never run or play. The editor shows a poster or a labeled placeholder and keeps the object on save.

Fonts

The editor uses font bytes to measure and render text consistently across machines with the same fonts.

• Embedded fonts (p:embeddedFontLst) are decoded in memory for one document. The editor honors their embedding permissions, and never writes them to disk or caches them across documents.
• Without other fonts, the editor uses metric-compatible substitutes from @docx-editor.dev/fonts. Compatible advance widths help preserve line breaks.
• You can supply your own font bytes. See Fonts.

The editor lists the families it substituted in snapshot().substitutedFonts, and PptxEditor.FontNotice shows them to the user.

Known approximations

These entries summarize rendering differences and behavior that ECMA-376 does not define precisely.

• Line model. Line heights and baselines use measured rules for Latin, Japanese, and Arabic text. Other scripts, vertical text, missing fonts, and overflowing centered or bottom-aligned text can shift baselines by several points.
• Long text clusters. Grapheme clusters longer than 256 UTF-16 units render in bounded pieces without shaping across piece boundaries. Surrogate pairs, source text, and caret boundaries stay intact.
• Glyph advances. Small glyph-width differences can shift aligned text or change line breaks near a box edge. Original and substitute fonts can use different kerning rules. Substitution fidelity is not measured against reference PDFs.
• Color transform spaces. a:tint, a:shade, and a:inv use linear RGB, and the a:lum* transforms use HSL. The other transforms are not measured against a reference.
• Gray transform. a:gray uses Rec. 709 weights on sRGB components. One measured color confirms it, so other weights are not ruled out.
• Blur. Shadow blur uses a Gaussian approximation measured against reference PDFs. Reflection blur uses a different, unmeasured radius. General blur requires @pptx-editor.dev/pro under the EigenPal Pro License.
• Shadow skew. kx and ky skew after the sx and sy scale, about the algn point.
• Glow and soft edge. These effects require @pptx-editor.dev/pro under the EigenPal Pro License; without it, they remain saved but invisible. Curved edges, sharp corners, and transparent fills can differ from the reference. Soft edges can remove thin details, and large radii are capped.
• Preset shadows. Preset shadows use measured silhouettes, including flattened perspective shadows and lighter copies for double shadows. Measurements cover all 20 presets at one distance. Other distances and colors remain unmeasured.
• 3-D shapes. 3-D rendering requires @pptx-editor.dev/pro under the EigenPal Pro License; without it, shapes render flat. Lighting, materials, bevels, and cameras are approximate, with perspective cameras rendered as parallel projections. Bottom bevels and 3-D text do not render; see 3-D effects.
• Effects not drawn. a:effectDag, group effects, text effects, and some fill overlays are not drawn. They stay in the file.
• Fill overlay. a:fillOverlay blends with the shape's own fill only. Over a semi-transparent fill, the result is opaque where the overlay is.
• Gradient colors. Two-stop gradients favor the brighter value of each color channel. Gradients with three or more stops interpolate linearly in sRGB.
• Path gradient focus. A circle path gradient draws as a focal radial gradient. A focus that is outside the circle or on it moves the circle out slightly.
• Gradient tiles. Tile rectangles set the bounds of circle and rectangle path gradients. A tile smaller than the shape renders once instead of repeating.
• Rectangle path gradients. path="rect" draws as four trapezoids. The joins along the diagonals can show seam pixels.
• Shape path gradients. path="shape" draws as bands of the outline, scaled about the focus. Steps between bands can show.
• Pattern tiles. Patterns use 8 × 8 pt tiles aligned to the slide grid, including on rotated or flipped shapes. All 54 preset patterns are measured against reference PDFs. Patterns in scaled groups, text, lines, table cells, and backgrounds remain unmeasured.
• Path fill modes. The darken and lighten path fill modes use fixed factors to shift colors toward black or white. ECMA-376 does not specify these factors.
• Fill rotation. Gradient and picture fills always turn with a rotated shape. rotWithShape="0" is ignored.
• Gradient text. A gradient on text spans the bounds of the whole text body.
• Tiled pictures. The tile size comes from the image's pixels and resolution, at 72 DPI when the image states none.
• Picture shape fill. A picture's own fill, behind the transparent areas of the image, is not drawn.
• Picture brightness and contrast. a:lum adds brightness to each component, then scales around mid-gray by contrast. The specification gives no formula, so washed-out pictures can draw lighter than expected.
• Picture recolor. Grayscale, duotone, and black and white take the luminance with Rec. 709 weights. The specification gives no weights.
• Dashes on picture borders. A picture's border draws outside the picture. Dashes get butt caps, and round dots draw as squares.
• EMF and WMF pictures. These pictures render as PNG at 192 DPI, capped at 4096 pixels per side. Text uses loaded fonts or substitutes, which can change its appearance. A placeholder appears during conversion, and high zoom can reveal pixels.
• Inset lines. a:ln/@algn="in" draws as a centered line. A picture's border always draws outside the picture.
• Hyperlink text. Link text draws in the theme hlink color with a single underline, unless the run states otherwise.
• Dash complexity. Outlines and table borders render solid when their estimated dash count exceeds 100,000. SVG and PDF use the same limit. Save preserves the original dash pattern.
• Compound lines. Compound line widths are measured on closed paths and straight lines. Curved, counterclockwise, self-crossing, capped, and dashed paths remain approximate. Complex open thick-thin lines can render as equal-width double lines.
• Paths without a move. A custom geometry path renders only if its first drawing command is a:moveTo. Later move commands do not repair an invalid start.
• Text in flipped shapes. Glyphs are never mirrored. Under a net horizontal flip, text stays upright. Under a net vertical flip, it turns 180°.
• Content placeholders. pic, tbl, and chart placeholders inherit the master's body placeholder and its text style. clipArt, dgm, and media placeholders inherit no master placeholder.
• Small caps. Lowercase letters draw at 80 % of the size.
• Underline styles. Underline styles other than sng and dbl draw as a single line. a:uLn is ignored.
• Missing glyphs. Characters missing from the selected font use a loaded fallback font. If no font contains a character, layout estimates its width. The estimate can change spacing and line breaks.
• East Asian, complex-script, and symbol fonts. Characters use their script font, with language settings controlling theme fonts and some shared characters. Missing glyphs use loaded fallback faces. Mixed fonts can shift baselines, and East Asian punctuation does not compress.
• Right-to-left text. The editor uses Unicode bidirectional layout, with some punctuation and caret-boundary differences. Arabic letters join in the editor but remain separate in PDF export, where they can overlap. See East Asian and complex-script text.
• Tab stops. Right, center, and decimal tab stops in right-to-left text, or in text that does not wrap, are not measured.
• Anchoring and alignment variants. anchorCtr is ignored, and justified or distributed vertical anchoring behaves as top anchoring. justLow and thaiDist use standard justification and distribution. These variants remain unmeasured.
• Upright East Asian text (eaVert). East Asian characters render upright without vertical font metrics or alternate glyphs. Rotated Latin characters can sit 1 pt off their baseline.
• Stacked text (wordArtVert, wordArtVertRtl). Stacked text places characters in square cells sized from the font. The text type controls whether columns progress left or right. Characters can sit up to 1.5 pt off across the line.
• Other vertical text types. mongolianVert uses rotated text with columns progressing from left to right. Mongolian vertical letter forms are not drawn. The editor cannot set this text type.
• Superscript and subscript. Raised and lowered text is two thirds of the run size.
• Bullets on aligned lines. On a centered or right-aligned line, the bullet moves with the text.
• Numbering schemes. All a:buAutoNum schemes render counters and punctuation, but reference measurements cover only selected schemes and values. Other schemes and larger values remain approximate. Unknown schemes use decimal numbering.
• Symbol font bullets. A Wingdings, Webdings, or Symbol bullet draws with that font. When the font is not available, the editor draws a Unicode character that looks the same.
• Trailing line break. A line break at the end of a paragraph adds an empty line, sized by the paragraph mark.
• Default table style. A missing definition for Medium Style 2 - Accent 1 uses the built-in version of that style.
• Rotated cell text. Vertical text in a table cell wraps at the row height and does not grow the row.
• Table cell effects. a:cell3D and table effects are not drawn.
• Coincident cell borders. Where two cells state different borders for one edge, the later cell in row order draws on top.
• Inconsistent cell merges. Merge markers outside a declared span render as normal cells. Spans stop at the table boundary or an earlier merged cell. These recovery rules are not measured against reference PDFs.
• Text warp. Warped text loses ligatures, complex-script shaping, and synthetic bold or italic; the caret and selection follow flat text. Vertical, rotated, diagram, and very long text render flat. Other warps can differ in spacing and placement; see Text warp.
• Diagram drawings. Diagrams display their saved drawing instead of regenerating their layout from data. Resizing the frame does not recalculate the drawing. Missing drawings or drawings above complexity limits show placeholders; see Diagrams.
• Equations. Equation spacing, baselines, and line heights are approximate, especially around display fractions and increased line spacing. Unsupported constructs or equations above complexity limits use the text box fallback. See Equations for editing and font requirements.

Approximations after editing

Edits recalculate the slide layout and apply text autofit rules. The following operations use approximations:

• Shape autofit. Text in rotated, multicolumn, or nonrectangular shapes uses an estimated size.
• Shrink on overflow. Each edit refits text from 100%, reducing line spacing and font size until it fits. Titles shrink to 90% at most, then overflow. Steps below 55% font scale are estimated, and trailing empty paragraphs do not affect the fit.
• Resize several shapes. Rotated shapes scale in the slide's axes.
• Ungroup a group with a non-uniform scale. Each child keeps its center, size, and rotation.
• Change case. A letter whose other case has a different length, such as ß, stays as it is. The language of the run is not used.
• Crop, Fill, Fit, Change Picture, Format Picture, and Reset Picture. In a group with a non-uniform scale, a crop is estimated. Fill and Fit center the crop on the image. Change Picture fits the new image in the old frame and removes the crop.
• Picture and shape presets. The Recolor, Corrections, Transparency, picture style, Shape Effects, and Shape Styles galleries write fixed preset definitions.
• Distribute. A turned object counts with its unrotated box.
• Flip and rotate in a group with a non-uniform scale. The result is estimated.
• Objects in mc:AlternateContent. The editor changes the branch it displays, with some edits also updating or removing alternate copies. Removing alternate copies can hide the object in readers that select another branch. Edits to a displayed fallback leave choice branches unchanged.
• Table frame size. After a table edit, the frame takes the laid-out table size. Row heights stay minimums.
• Insert table. A new table fills an available content or table placeholder. Without one, it appears in the center of the slide.
• Split cells. New columns and rows share the width or height of the cell they split.

Approximations of the PDF export

@pptx-editor.dev/pptx-to-pdf paints the same layout as the editor, so the approximations above apply to it too. Export-specific approximations report diagnostic codes. See PDF export for usage and diagnostics.

• Shadow and glow blur. Drawn as layers of growing outlines, not as a Gaussian blur.
• Opaque silhouettes. Fill transparency does not lighten a shadow, and a picture's shadow takes the shape of its frame.
• Inner shadows. The outer half of an outline is not shaded, and an unfilled shape gets no inner shadow.
• Soft edges. Drawn hard.
• Blur. a:blur is not drawn.
• Reflection blur. A reflection is drawn with its fade, without its blur.
• Gradient lines. Drawn in one color.
• Gradient stops. At most 64 stops are drawn.
• Fills outside the box. A rectangle path gradient or a picture fill paints the shape's box only.
• Tiled pictures. Drawn stretched over the box.
• Picture color effects. Grayscale, duotone, brightness and contrast, and black and white are not applied.
• Compound lines. Dashed compound lines and compound table borders render as single lines. Compound bands requiring more than 16,384 points also render as single lines.
• SVG pictures. The PNG fallback of the picture is drawn.
• Text. Synthetic bold and italic do not render, upright vertical characters rotate, and missing glyphs disappear. Underline styles other than single and double render as single lines.
• Not drawn. Text patterns, line patterns, picture-filled text, and text outlines do not render. Unsupported picture formats and frames without usable drawings, pictures, or grids do not render. Unsupported charts show placeholders; see Charts.

See also

• Fonts: load font bytes and choose font sources.
• Tables: edit tables with editor commands.
• Customization: change the toolbar, menus, dialogs, and appearance.