Common errors and how to fix them
Most problems do not stop the document: unknown commands are skipped and listed in the Problems tab, a formula that cannot be read is shown in red and named there, and missing images or citations are marked in place; only an EPS image stops the whole document.
How problems are reported
A TeX installation stops at the first error and asks you what to do. Scissor LaTeX keeps going: it typesets as much of the document as it can and lists what it could not handle in the Problems tab under the preview. Each entry has the line it refers to where that is known, and clicking it jumps there.
There are four kinds of result:
| What you see | What it means | Where to look |
|---|---|---|
| A message in the Problems tab, document fine | Something was skipped or left out. | The sections below. |
| A formula shown as red source code | That formula could not be read. | Red formulas |
A red [key?] or a grey dashed box | A citation or an image is missing. | Missing citations and images |
| No pages at all, an error at the top | The whole document failed. | When the whole document does not typeset |
"Skipped N unknown commands"
This is the message you will see most often, and the counterpart of LaTeX's "Undefined control sequence". A command that Scissor LaTeX does not know is skipped: its name disappears, and the text in its braces stays.
An unknown command: the name goes, the text stays
The value is \highlightvalue{44} and the unit is \unitname{kg}.Problems tab: Skipped 2 unknown commands: \highlightvalue, \unitname
What to do:
- Check the spelling.
\textbfworks,\textbolddoes not. - If the command comes from a package, look the package up in the package pages. Some commands have a simple replacement.
- If it is your own command, check that it is defined with
\newcommandbefore it is used (see Your own commands).
An unknown environment is different: it is removed silently and its content stays, with no message. If text looks unformatted, check the environment name.
"Package ... is not available here"
\usepackage never fails. A package that Scissor LaTeX does not know is noted in the Problems tab, and its formatting is not applied. The rest of the document typesets as usual, and commands from the package that are not known are reported as unknown.
A package that is not available
\documentclass{article}
\usepackage{fancyboxes2}
\begin{document}
The document still typesets.
\end{document}Problems tab: Package fancyboxes2 isn't supported in the preview, so its formatting is not applied. If it is your own package, add fancyboxes2.sty to the project.
Red formulas
When a formula contains something the math converter cannot read, that formula is shown as red source code. The rest of the document is not affected. The Problems tab names the formula, its line and the reason, such as "This formula could not be read: \symbf{v} (unknown command: \symbf)"; after ten formulas, one more line gives the count of the rest.
\symbf is not available, so the formula is red
The vector $\symbf{v}$ is shown in red,
while $\boldsymbol{v}$ next to it works.Shown in red: the formula cannot be read, so its source is shown instead.
Common causes and fixes:
| Cause | Fix |
|---|---|
\abs{x}, \norm{x}, \dv{f}{x} (physics) | \left\lvert x \right\rvert, \left\lVert x \right\rVert, \frac{df}{dx} |
\SI{44}{\kilo\gram} (siunitx) | 44\,\mathrm{kg} |
\sideset | Rewrite the formula without it. |
A $ without its partner | Close the formula. An unclosed $ is not red: it turns the rest of its paragraph into run-together italic math, up to the next blank line. |
Missing citations and images
A citation key that is not in any .bib file prints as a red [key?], and the Problems tab lists the missing keys. A missing image becomes a grey dashed box with the file name.
An image that is not in the project
\begin{figure}[h]
\centering
\includegraphics[width=0.5\linewidth]{figures/plot.png}
\caption{A plot that has not been uploaded yet.}
\end{figure}
Problems tab: Images not in the project: figures/plot.png
Upload the file to the project with the same path, or fix the path. Without an extension, .png, .jpg, .jpeg and .svg files are found; PDF and EPS figures show the box as well (see Figures and images). For citations, see Bibliographies and citations.
Other messages
| Message | Meaning | What to do |
|---|---|---|
| "N included files are not part of this conversion" | \subfile, \import, \lstinputlisting, \inputminted or \includepdf was skipped. | Use \input, or paste the content in. |
| "File not found: ..." | An \input or \include names a file that is not in the project. | Check the path from the project's top folder. |
| "N pictures of an unsupported kind are not included" | A tikzcd, circuitikz, forest or picture environment was left out. | See Drawings with TikZ. |
| "TikZ option '...' is not supported yet" | A picture uses an option the drawing engine does not know. The picture is drawn without it. | Check the option, or leave it out. |
| "Layout in the style of ... Not official." | A conference class or package switched to a look-alike layout. | Nothing; this is information. |
| "Macro expansion stopped at the safety limit" | A command expands into itself, or into a huge amount of text. | Look for a \newcommand that uses its own name. |
| "This formula could not be read: ..." | The formula is shown in red; the reason is in brackets. | See Red formulas. |
| "References to labels that do not exist (shown as ??): ..." | A \ref, \eqref, \pageref or \cref names a label that is not defined, or one on a red formula. | Check the spelling of the label. |
| "Bibliography style ... is not available; using numbered references [1] instead" | \bibliographystyle names a style that is not on the list, such as alpha. | Pick a style from the list, or keep the numbered references. |
| "Skipped .bib entries: ..." | These entries of the .bib file could not be read (a missing brace, a duplicate key); the others are used. | Fix the entry at the line given. |
LaTeX errors you will not see here
Some classic LaTeX errors do not stop anything in Scissor LaTeX, which makes them easy to miss:
| LaTeX error | What Scissor LaTeX does |
|---|---|
"Missing $ inserted" for x_1 in text | Prints x_1 literally. Put math in $...$. |
| "Misplaced alignment tab character &" | Prints & literally. Write \& for an ampersand. |
| "Extra }, or forgotten $" | Ignores unbalanced braces. |
| "\begin{itemize} ended by \end{document}" | Closes the environment for you. |
| "Reference ... undefined" | Prints a bold ??; the Problems tab lists the missing labels. |
Text that LaTeX would reject
Fish & chips cost 44 dollars, and x_1 is not a formula here.
Write Fish \& chips and $x_1$ instead.These documents may still fail in a TeX installation, so fix them even though the preview looks fine.
What differs from a TeX installation
For a checklist by symptom, see Troubleshooting.
Questions and answers
What does "Undefined control sequence" mean?
LaTeX does not know a command, usually because of a typo or a missing package. In Scissor LaTeX the same situation shows as "Skipped N unknown commands" in the Problems tab, and the document still typesets.
Why is my formula red?
The formula contains a command that the math converter does not know, such as \symbf or \abs. The Problems tab names it. Replace that command; the table on this page lists common replacements.
Why do I see [key?] in my document?
The citation key is not in any .bib file of the project. Check the spelling and that the .bib file is uploaded.
Every example on this page is typeset by Scissor LaTeX when the site is built. Last updated 2026-11-07.