It may seem like magic when you get a response from us here at Overleaf with a precise solution to a problem with your project. In reality, we've accumulated a few tips and tricks that we use to help us identify and solve LaTeX problems, and we'd like to share some of the most common ones with you in this post.

1. Is there an error or warning? Start by looking at the "Logs and output files" icon, just to the right of the Recompile button.

Warning messages are shown in orange. These are often just alerts that LaTeX has found something out of the ordinary, and has made automated adjustments. They may not have an impact on the final look of your document, and can be ignored unless you also want perfect markup behind-the-scenes. For example, many float and margin/space issues are corrected by LaTeX with no need for user correction.

Error messages are shown in red. They are usually more problematic and prevent the document from properly compiling, or indicate a bigger problem. You should fix errors in almost all cases.

2. Does the document fully compile?

If the document still compiles despite the error indication, you may think you don't need to worry about it, or you may want to postpone troubleshooting while you work on the content of your document. But we would recommend addressing errors soon after they are introduced. If several errors build up, it can become difficult to determine the cause of the problems, and too many errors building up can lead to compiler timeouts.

Keep in mind also that even if a PDF is produced, if there are compiler errors, the PDF may not contain what you expect. If you have an error message, or a warning message and the document is not compiling, it is time to investigate further.

3. Does the message indicate a specific error or line number?

In many cases, the LaTeX engine is smart enough to figure out the exact error and give you a line number. In the example above, there was a symbol "$", which LaTeX requires you to escape like this: "\$". The error message even indicates that the error is on line 15, highlights the appropriate line, and shows an excerpt of the text where the problem was located. You can click on the error message to jump directly to the file and line number where the error occurs in the source code.

If no line number is indicated, continue trying some of the steps below.

4. Is a specific error message provided that might give clues?

In the partial example error message above, no line number is given, but the message gives a clue that the error preventing compilation is a BibTeX problem. You may be able to figure out from the text of the rest of the message that this is because the .bib file is empty or the main.tex file did not call a bibliography. If the error is not obvious, proceed.

5. Is it a compilation "timeout" error?

In some cases, users may face timeout compilation errors under certain conditions. This is due to resource/compilation time limits on our servers. We have different time limits for free accounts and paid accounts, and depending if you are logged in to the Overleaf.com site or not. There are a number of tips we have in order to make your document compile faster, and if these don't work, feel free to contact us with a support request.

6. Try the forums!

If no line number is given and you aren't able to decipher the given error message, a quick "copy-paste" trip to your favorite search engine may reveal information from more expert users who have faced a similar issue. Some excellent TeX related forums include LaTeX Stack Exchange and LaTeX Community.

7. Inspect the full log file

If you've tried all of the above and exhausted all of the error and warning message information, but you're still in the dark, it's time to look at the entire log file. At the bottom of the message dialogue box at the top right of your screen, you have the option of clicking to go to first error / warning or open latex log. Choose the latter, and click to download the .log file from your document's failed compilation. Open it with a text editor and read carefully from the end of the document to the beginning, looking for possible errors. Look for keywords like warning or error, message clues, and document names / line numbers where available. Also use a search engine and forums to help understand messages. Sometimes the log contains more specific information than the briefer message dialogues.

8. Compare previous versions and roll back changes

Have you made any major changes to the text of your document? Have you installed any new packages with \usepackage{}, or made other edits to your preface? If your project was compiling just fine previously, then you've likely introduced an error into the project in your recent edits. In Overleaf, there are two ways to roll back recent changes. These are versions and history.

The versions feature allows you to explicitly save versions of your document and experiment with edits, with the ability to compare various versions, and restore to an earlier version. You can access this feature with the Versions button at the top left of the Overleaf page, above the editor.

If you haven't saved any versions, or haven't done so recently, click the history button shown above, which is directly above the text editor, next to the comment button.

The history feature allows you to access a 24 hour history of recent changes to your project and documents. In cases where you need to go back further in time, contact us with a support request and we may be able to recover an older version.

9. Try moving \end{document}

If you still haven't narrowed it down, try this little tip. Cut the text: \end{document} from the very end of your main .tex file and try pasting it and undoing again and again in various parts of your project. Start with the main .tex file, and then if necessary any sub-files that you call in your main file with \input{} or \include{}. Move in a methodical fashion from the very end of the project/document toward the beginning of the document, repeating this process one section at a time. Pay particular attention to equations or other complicated sections prone to small errors.

This tip should help you limit your document progressively to a smaller and smaller document until you are able to isolate the section containing the error. If the document suddenly begins compiling, you know you've located the erroneous section. In many cases the problem could be something as simple as a mis-typed command, an un-escaped special character, or a missing bracket.

On occasion, you may find an error or warning message, or a statement in your log file indicating that there is a problem in an auxiliary file with an extension other than .tex, such as .bbl, .aux, etc. In these cases, inspecting the offending auxiliary file may lead you to the source of the problem in the main .tex and .bib files. This is particularly common with tricky BibTeX errors, where an error indicates a problem in the .bbl file, which is an intermediary file created from the .bib file and .tex file during the compilation process.

If this is the case, you can click the Download as ZIP button on the bottom left of the project files menu, above the Dropbox button. Choose Input and Output Files as shown in the example above, and download a .zip file to your computer that contains all of your original input files, as well as auxiliary and output files created during attempted compilation. Then you can open the possible culprit file in a text editor and search for the problem you identified. Often, this will indicate a line number or a bit of text you can search in the original file.

11. Try compiling locally

If you have a version of LaTeX, preferably TeXLive, installed on your computer, can also try compiling your project locally in the TeX editor of your choice. This is particularly important when you have exhausted all the other possibilities and suspect that it might be a particular issue with our site itself. In our experience, most errors and warnings are LaTeX issues, and site-specific LaTeX problems are quite rare. This is because we use a standard installation of the latest full version of TeXLive on the latest Long-Term Support version of Ubuntu Linux. If you don't have a local version of LaTeX installed, we're happy to test this for you.

If your document compiles locally, but not on Overleaf, the most common causes are compilation timeouts, or the use of uncommon templates or packages that do not come standard with TeXLive. See here, for more details on compilation timeout errors. And if you have your own packages or templates, which do not come standard with TeXLive, you can always upload them to your project folder and call them in the same fashion with \usepackage{}.