[Tex/LaTex] Package biblatex Warning: Data encoding is ‘utf8’. Use backend=biber

biberbiblatexwarnings

After a few days break I went back to working on a report. When I tried to compile I got the following warning:

Package biblatex Warning: Data encoding is 'utf8'.
(biblatex)                Use backend=biber.

I haven't changed a thing since last week, when it worked. I did open the file on someone else's laptop, but didn't touch the code. I am using ShareLaTeX. The relevant code is (I think):

\documentclass[11pt]{report}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\graphicspath{ {images/} }

\usepackage[a4paper,width=150mm,top=25mm,bottom=25mm]{geometry}
\usepackage{float}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[backend=bibtex,style=authoryear,sorting=none]{biblatex}
\addbibresource{references.bib}

\printbibliography

References are in the form of:

@book{griffiths,
    author        = {D.J. Griffiths},
    title         = {Introduction to Quantum Mechanics},
    year          = {2005},
    publisher     = {Pearson Education Inc.},
    location      = {USA, New Jersey, Upper Saddle River}
}

EDIT: When I change the backend to biber, the file doesn't recognise any references, and the log says:

Package biblatex Warning: Please (re)run Biber on the file:
(biblatex)                output
(biblatex)                and rerun LaTeX afterwards.

I'm unsure how to do this in ShareLaTeX. Consider me a simple mortal, who is not knowledgeable about much outside of basic report writing.

Best Answer

The answer is in the comments, but since nobody wrote an complete answer, I will.

Bibtex requires ascii encoding. If your document is set to utf8 encoding, bibtex will assume the bib file also is utf8. Therefore, you have to be sure your bib file is ascii encoded, and you have to tell bibtex to consider it as ascii.

In your case, biblatex package should be loaded with the following options:

\usepackage[backend=bibtex,bibencoding=ascii,style=authoryear,sorting=none]{biblatex}

The other option is to use biber as backend. In that case, the bib file can be utf8 encoded.

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