This might be an known limitation in tex4ht, I do not know. But this MWE below gives the error

! Package amsmath Error: \tag not allowed here.

Only when run with make4ht. No error with lualatex nor with pdflatex.


x=y \tag{1}

The output is

>make4ht  foo.tex
LaTeX2e <2017/01/01> patch level 3
Babel <3.9r> and hyphenation patterns for 83 language(s) loaded.
(./foo.tex (/usr/local/texlive/2016/texmf-dist/tex/latex/base/article.cls
Document Class: article 2014/09/29 v1.4h Standard LaTeX document class

! Package amsmath Error: \tag not allowed here.

See the amsmath package documentation for explanation.
Type  H <return>  for immediate help.
l.7 x=y \tag

List files

*File List*
 article.cls    2014/09/29 v1.4h Standard LaTeX document class
  size11.clo    2014/09/29 v1.4h Standard LaTeX file (size option)
 amsmath.sty    2016/11/05 v2.16a AMS math features
 amstext.sty    2000/06/29 v2.01 AMS text
  amsgen.sty    1999/11/30 v2.0 generic functions
  amsbsy.sty    1999/11/29 v1.2d Bold Symbols
  amsopn.sty    2016/03/08 v2.02 operator names


which make4ht

Is the above known issue with make4ht? What should I do to workaround this? Do I need to change \[..\] to \begin{align}....\end{align} to use \tag{} with tex4ht? No error there with make4ht. Only error when using tag with \[..\]

  • 3
    Generally, \[...\] used for the unnumbered display equation, may be the error due to that tag, as you suggested, change the same to align environment then check the same...
    – MadyYuvi
    Jul 25, 2017 at 9:53
  • 1
    @MadyYuvi -- please not align! single-line equations should use the equation environment. (the spacing above and below is calculated differently for equation and align.) Jul 25, 2017 at 14:36
  • @MadyYuvi But for one equation I've always used \[...\] and not align. Also there is no error with lualatex nor with pdflatex using tag with \[...\]. I've also seen tag used with \[...\] by Latex experts. For example this accepted answer adding-letters-to-equation-numbers uses tag with \[...\]
    – Nasser
    Jul 25, 2017 at 18:10

1 Answer 1


Amsmath rededines \[ and \] to produce \begin{equation*} resp. \end{equation*}. tex4ht redefines it to something different, so the \tag doesn't work here anymore. You can try the amsmath definitions yourself:



This is a result:

enter image description here

  • 1
    Why don't we update the amsmath.sty in tex4ht to include these \DeclareRobustCommand's?
    – Yai0Phah
    Jan 24, 2019 at 19:02
  • @FrankScience I cannot get it to work correctly, it clashes with some options
    – michal.h21
    Jan 24, 2019 at 20:05

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .