LaTeX/Hyperlinks

LaTeX enables typesetting of hyperlinks, useful when the resulting format is PDF, and the hyperlinks can be followed. It does so using the package hyperref.

Hyperref

The package hyperref provides LaTeX the ability to create hyperlinks within the document. It works with pdflatex and also with standard "latex" used with dvips and ghostscript or dvipdfm to build a PDF file. If you load it, you will have the possibility to include interactive external links and all your internal references will be turned to hyperlinks. The compiler pdflatex makes it possible to create PDF files directly from the LaTeX source, and PDF supports more features than DVI. In particular PDF supports hyperlinks. Moreover, PDF can contain other information about a document such as the title, the author, etc., which can be edited using this same package.

Usage

The basic usage with the standard settings is straightforward. Just load the package in the preamble:

\usepackage{hyperref}

This will automatically turn all your internal references into hyperlinks. It won't affect the way to write your documents: just keep on using the standard \label-\ref system (discussed in the chapter on Labels and Cross-referencing); with hyperref those "connections" will become links and you will be able to click on them to be redirected to the right page. Moreover the table of contents, list of figures/tables and index will be made of hyperlinks, too. The hyperlinks will not show up if you are working in draft mode.

Commands

The package provides some useful commands for inserting links pointing outside the document.

\hyperref

Usage:

\hyperref[label_name]{''link text''}

This will have the same effect as \ref{label_name} but will make the text link text a full link, instead. The two can be combined. If the lemma labelled as mainlemma was number 4.1.1 the following example would result in

We use \hyperref[mainlemma]{lemma \ref*{mainlemma} }.

We use lemma 4.1.1.

with the hyperlink as expected. Note the "*" after \ref for avoiding nested hyperlinks.

\url

Usage:

\url{<my_url>}

It will show the URL using a mono-spaced font and, if you click on it, your browser will be opened pointing at it.

\href

Usage:

\href{<my_url>}{<description>}

It will show the string description using standard document font but, if you click on it, your browser will be opened pointing at my_url. Here is an example:

\url{https://www.wikibooks.org} \href{https://www.wikibooks.org}{Wikibooks home}

Both point at the same page, but in the first case the URL will be shown, while in the second case the URL will be hidden. Note that, if you print your document, the link stored using \href will not be shown anywhere in the document.

Other possibilities

Apart from linking to websites discussed above, hyperref can be used to provide mailto links, links to local files, and links to anywhere within the PDF output file.

E-mail address

A possible way to insert email links is by

\href{mailto:my_address@wikibooks.org}{my\_address@wikibooks.org}

It just shows your email address (so people can know it even if the document is printed on paper) but, if the reader clicks on it, (s)he can easily send you an email. Or, to incorporate the url package's formatting and line breaking abilities into the displayed text, use

\href{mailto:my_address@wikibooks.org}{\nolinkurl{my_address@wikibooks.org} }

When using this form, note that the \nolinkurl command is fragile and if the hyperlink is inside of a moving argument, it must be preceded by a \protect command.

Local file

Files can also be linked using the url or the href commands. You simply have to add the string run: at the beginning of the link string:

\url{run:/path/to/my/file.ext} \href{run:/path/to/my/file.ext}{text displayed}

Following http://tex.stackexchange.com/questions/46488/link-to-local-pdf-file the version with url does not always work, but href does.

It is possible to use relative paths to link documents near the location of your current document; in order to do so, use the standard Unix-like notation (./ is the current directory, ../ is the previous directory, etc.)

Examples:

\href{run:D:/my_folder/my_subfolder/my_file.txt}{Windows, absolute path} \href{run:my_subfolder/my_file.txt}{Windows, relative path} \href{run:./my_subfolder/my_file.txt}{Windows, relative path, variant} \href{run:/my_folder/my_subfolder/my_file.txt}{Linux, absolute path} \href{run:./my_subfolder/my_file.txt}{Linux, relative path}

Hyperlink and Hypertarget

It is also possible to create an anchor anywhere in the document (with or without caption) and to link to it. To create an anchor, use:

\hypertarget{label}{target caption}

and to link to it, use:

\hyperlink{label}{link caption}

where the target caption and link caption are the text that is displayed at the target location and link location respectively.

Note also that if you put a hypertarget, when clicking a link to that hypertarget, it may actually direct to the line after the hypertarget, which is not desirable. Therefore if this occurs, you can report the bug and refer to here for a solution.

Viewing in a browser

You can also get an external URL to the hypertarget by appending #label to the URL for the file, or right clicking one of the hyperlinks to the target and copying the URL, or getting the link from the headings in the sidebar of the PDF, or through a process of deduction from viewing (e.g. subsubsection 11.5.1 would have the label subsubsection.11.5.1). This can be useful e.g. for academic and pedagogical purposes. The URL will then direct to the target if you enable a PDF viewer that is compatible with PDF 1.5 in a browser, such as PDF Viewer for Chrome or Chromium browsers, and No PDF Download for Firefox; and on Android the Xodo app works best with links as it renders them with the correct border as with PDF desktop programs, followed by the Foxit PDF app which renders links highlighted in grey (while in other apps links may also work but without any special rendering, such as the Dropbox PDF viewer app; and yet others do not work with links, e.g Drive PDF viewer, PDF reader and Google PDF viewer). You may need to open the URL to the PDF in a new tab, otherwise it may prompt to download it (i.e. if you are clicking on the URL, don't left click, right click and select to open it in a new tab).

Customization

The standard settings should be fine for most users, but if you want to change something, that is also possible. There are several variables and two methods to pass those to the package. Options can be passed as an argument of the package when it is loaded (the standard way packages work), or the \hypersetup command can be used as follows:

\hypersetup{<option1> [, ...]}

you can pass as many options as you want; separate them with a comma. Options have to be in the form:

variable_name=new_value

exactly the same format has to be used if you pass those options to the package while loading it, like this:

\usepackage[<option1, option2>]{hyperref}

Here is a list of the possible variables you can change (for the complete list, see the official documentation). The default values are written in an upright font:

Checkout 3.8 Big list at hyperref-manual at tug.org

variable	values	comment
bookmarks	=true,false	show or hide the bookmarks bar when displaying the document
unicode	=false,true	allows to use characters of non-Latin based languages in Acrobat’s bookmarks
pdfborder	={RadiusH RadiusV Width [Dash-Pattern]}	set the style of the border around a link. The first two parameters (RadiusH, RadiusV) have no effect in most pdf viewers. Width defines the thickness of the border. Dash-Pattern is a series of numbers separated by space and enclosed by box-brackets. It is an optional parameter to specify the length of each line & gap in the dash pattern. For example, {0 0 0.5 [3 3]} is supposed to draw a square box (no rounded corners) of width 0.5 and a dash pattern with a dash of length 3 followed by a gap of length 3. There is no uniformity in whether/how different pdf viewers render the dash pattern.
pdftoolbar	=true,false	show or hide Acrobat’s toolbar
pdfmenubar	=true,false	show or hide Acrobat’s menu
pdffitwindow	=true,false	resize document window to fit document size
pdfstartview	={FitH},{FitV},etc.	fit the width of the page to the window
pdftitle	={text}	define the title that gets displayed in the "Document Info" window of Acrobat
pdfauthor	={text}	the name of the PDF’s author, it works like the one above
pdfsubject	={text}	subject of the document, it works like the one above
pdfcreator	={text}	creator of the document, it works like the one above
pdfproducer	={text}	producer of the document, it works like the one above
pdfkeywords	={text}	list of keywords, separated by commas, example below
pdfnewwindow	(=true,false)	define if a new PDF window should get opened when a link leads out of the current document. NB: This option is ignored if the link leads to an http/https address.
pagebackref	(=false,true)	activate back references inside bibliography. Must be specified as part of the \usepackage{} statement.
colorlinks	(=false,true)	surround the links by color frames (false) or colors the text of the links (true). The color of these links can be configured using the following options (default colors are shown):
hidelinks		hide links (removing color and border)
linkcolor	=red	color of internal links (sections, pages, etc.)
linktoc	=none,section,page,all	defines which part of an entry in the table of contents is made into a link
citecolor	=green	color of citation links (bibliography)
filecolor	=cyan	color of file links
urlcolor	=magenta	color of URL links (mail, web)
linkbordercolor	={1 0 0}	color of frame around internal links (if colorlinks=false)
citebordercolor	={0 1 0}	color of frame around citations
urlbordercolor	={0 1 1}	color of frame around URL links

Please note, that explicit RGB specification is only allowed for the border colors (like linkbordercolor etc.), while the others may only assigned to named colors (which you can define your own, see Colors). In order to speed up your customization process, here is a list with the variables with their default value. Copy it in your document and make the changes you want. Next to the variables, there is a short explanations of their meaning:

\hypersetup{ bookmarks=true, % show bookmarks bar? unicode=false, % non-Latin characters in Acrobat’s bookmarks pdftoolbar=true, % show Acrobat’s toolbar? pdfmenubar=true, % show Acrobat’s menu? pdffitwindow=false, % window fit to page when opened pdfstartview={FitH}, % fits the width of the page to the window pdftitle={My title}, % title pdfauthor={Author}, % author pdfsubject={Subject}, % subject of the document pdfcreator={Creator}, % creator of the document pdfproducer={Producer}, % producer of the document pdfkeywords={keyword1, key2, key3}, % list of keywords pdfnewwindow=true, % links in new PDF window colorlinks=false, % false: boxed links; true: colored links linkcolor=red, % color of internal links (change box color with linkbordercolor) citecolor=green, % color of links to bibliography filecolor=cyan, % color of file links urlcolor=magenta % color of external links }

If you don't need such a high customization, here are some smaller but useful examples. When creating PDFs destined for printing, colored links are not a good thing as they end up in gray in the final output, making it difficult to read. You can use color frames, which are not printed:

\usepackage{hyperref} \hypersetup{colorlinks=false}

or make links black:

\usepackage[hidelinks]{hyperref}

or use \usepackage{hyperref} \hypersetup{hidelinks}

When you just want to provide information for the Document Info section of the PDF file, as well as enabling back references inside bibliography:

\usepackage[pdfauthor={Author's name},% pdftitle={Document Title},% pagebackref=true,% pdftex]{hyperref}

By default, URLs are printed using mono-spaced fonts. If you don't like it and you want them to be printed with the same style of the rest of the text, you can use this:

\urlstyle{same}

Troubleshooting

Problems with Links and Equations 1

Messages like the following

! pdfTeX warning (ext4): destination with the same identifier (name{
equation.1.7.7.30}) has been already used, duplicate ignored

appear, when you have done something like

\begin{eqnarray}a=b\nonumber\end{eqnarray}

The error disappears, if you use instead this form:

\begin{eqnarray*}a=b\end{eqnarray*}

Beware that the shown line number is often completely different from the erroneous line.

Possible solution: Place the amsmath package before the hyperref package.

Problems with Links and Equations 2

Messages like the following

! Runaway argument?
{\@firstoffive }\fi ), Some text from your document here (\ref {re\ETC.
Latex Error: Paragraph ended before \Hy@setref@link was complete.

appear when you use \label inside an align environment.

Possible solution: Add the following to your preamble:

\AtBeginDocument{\let\textlabel\label}

Note: The same error appears if you use a colon ":" as part of a label, i.e. \label{lst:program01}. Replacing that will help.

Problems with Links and Pages

Messages like the following:

! pdfTeX warning (ext4): destination with the same
identifier (name{page.1}) has been already used,
duplicate ignored

appear when a counter gets reinitialized, for example by using the command \mainmatter provided by the book document class. It resets the page number counter to 1 prior to the first chapter of the book. But as the preface of the book also has a page number 1 all links to "page 1" would not be unique anymore, hence the notice that "duplicate has been ignored." The counter measure consists of putting plainpages=false into the hyperref options. This unfortunately only helps with the page counter. An even more radical solution is to use the option hypertexnames=false, but this will cause the page links in the index to stop working.

The best solution is to give each page a unique name by using the \pagenumbering command:

\pagenumbering{alph} % a, b, c, ... ... titlepage, other front matter ... \pagenumbering{roman} % i, ii, iii, iv, ... ... table of contents, table of figures, ... \pagenumbering{arabic} % 1, 2, 3, 4, ... ... beginning of the main matter (chapter 1) ...

Another solution is to use \pagenumbering{alph} before the command \maketitle, which will give the title page the label page.a. Since the page number is suppressed, it won't make a difference to the output.

By changing the page numbering every time before the counter is reset, each page gets a unique name. In this case, the pages would be numbered a, b, c, i, ii, iii, iv, v, 1, 2, 3, 4, 5, ...

If you don't want the page numbers to be visible (for example, during the front matter part), use \pagestyle{empty} ... \pagestyle{plain}. The important point is that although the numbers are not visible, each page will have a unique name.

Another more flexible approach is to set the counter to something negative:

\setcounter{page}{-100} ... titlepage, other front matter ... \pagenumbering{roman} % i, ii, iii, iv, ... ... table of contents, table of figures, ... \pagenumbering{arabic} % 1, 2, 3, 4, ... ... beginning of the main matter (chapter 1) ...

which will give the first pages a unique negative number.

The problem can also occur with the algorithms package: because each algorithm uses the same line-numbering scheme, the line identifiers for the second and follow-on algorithms will be duplicates of the first.

The problem occurs with equation identifiers if you use \nonumber on every line of an eqnarray environment. In this case, use the *'ed form instead, e.g. \begin{eqnarray*} ... \end{eqnarray*} (which is an unnumbered equation array), and remove the now unnecessary \nonumber commands.

If your url's are too long and running off of the page, try using the breakurl package to split the url over multiple lines. This is especially important in a multicolumn environment where the line width is greatly shortened.

Problems with bookmarks

The text displayed by bookmarks does not always look like you expect it to look. Because bookmarks are "just text", much fewer characters are available for bookmarks than for normal LaTeX text. Hyperref will normally notice such problems and put up a warning:

Package hyperref Warning:
Token not allowed in a PDFDocEncoded string:

You can now work around this problem by providing a text string for the bookmarks, which replaces the offending text:

\texorpdfstring{''TEX text''}{''Bookmark Text''}

Math expressions are a prime candidate for this kind of problem:

\section{ \texorpdfstring{$E=mc^2$}{E=mc2} }

which turns \section{$E=mc^2$} to E=mc2 in the bookmark area. Color changes also do not travel well into bookmarks:

\section{ \textcolor{red}{Red !} }

produces the string "redRed!". The command \textcolor gets ignored but its argument (red) gets printed. If you use:

\section{ \texorpdfstring{\textcolor{red}{Red !}}{Red\ !} }

the result will be much more legible.

If you write your document in unicode and use the unicode option for the hyperref package you can use unicode characters in bookmarks. This will give you a much larger selection of characters to pick from when using \texorpdfstring.

Problems with tables and figures

The links created by hyperref point to the label created within the float environment, which, as previously described, must always be set after the caption. Since the caption is usually below a figure or table, the figure or table itself will not be visible upon clicking the link. A workaround exists by using the package hypcap [2] with:

\usepackage[all]{hypcap}

Be sure to call this package after loading hyperref.

If you use the wrapfig package mentioned in the "Wrapping text around figures" section of the "Floats, Figures and Captions" chapter, or other similar packages that define their own environments, you will need to manually include \capstart in those environments, e.g.:

\begin{wrapfigure}{R}{0.5\textwidth} \capstart \begin{center} \includegraphics[width=0.48\textwidth]{filename} \end{center} \caption{\label{labelname}a figure} \end{wrapfigure}

Problems with long caption and \listoffigures or long title

There is an issue when using \listoffigures with hyperref for long captions or long titles. This happens when the captions (or the titles) are longer than the page width (about 7-9 words depending on your settings). To fix this, you need to use the option breaklinks when first declaring:

\usepackage[breaklinks]{hyperref}

This will then cause the links in the \listoffigures to word wrap properly.

Problems with already existing .toc, .lof and similar files

The format of some of the auxiliary files generated by latex changes when you include the hyperref package. One can therefore encounter errors like

! Argument of \Hy@setref@link has an extra }.

when the document is typeset with hyperref for the first time and these files already exist. The solution to the problem is to delete all the files that latex uses to get references right and typeset again.

Problems with footnotes and special characters

See the relevant section.

Problems with Beamer

Using the command

\hyperref[some_label]{some text}

is broken when pointed at a label. Instead of sending the user to the desired label, upon clicking the user will be sent to the first frame. A simple work around exists; instead of using

\phantomsection\label{some_label}

to label your frames, use

\hypertarget{some_label}{}

and reference it with

\hyperlink{some_label}{some text}

Problems with draft mode

WARNING! Please note that if you have activated the "draft"-option in your \documentclass declaration the hyperlinks will not show up in the table of contents, or anywhere else for that matter!!!

The hyperlinks can be re-enabled by using the "final=true" option in the following initialization of the hyperref package, just after the package was included:

\usepackage{hyperref} \hypersetup{final=true}

A good source of further options for the hyperref package can be found here .