I fully agree with planetmaker's answer. I just want to add, that there are also regional differences. I live in Austria, and the most common version here is
All other predicates mentioned by planetmaker are also in use in Austria.
But there is an interesting issue with the German words for the noun check (or checkmark):
The check-symbol (the sign ✓) is called »Hakerl« in Austria (and also in Bavaria as I believe) but »Häkchen« in non-Bavarian Germany.
(I guess it could be »Häkli« in Switzerland and parts of Germany with Alemannic dialects, but I don't know much about Alemannic dialects and colloquial speech, so there is a high chance that my guess is not correct.)
But we in Austria have a severe problem with Hakerl/Häkchen: The word »Hakerl« is clearly considered to be a part of colloquial language. It doesn't belong to Austrian Standard German or any other standard variation of German language. This is why »Hakerl« is not listed in Duden, DWDS, Wiktionary or any other notable dictionary about Standard German. So, in Austria we use »Hakerl« a lot in spoken language, but we avoid it in written texts because it feels wrong to write colloquial terms.
Exceptions exist but are rare:
Leitbild Ried 2020: "Können viele Hakerl setzen"
AMS: Mann vergisst Hakerl auf Formular und verliert 600 Euro
Das Konto „ElonMuskoffici“ hatte ein offizielles Verifizierungs-Hakerl, ...
Was das neue Hakerl bei WhatsApp bedeutet
Kreuzerl, Hakerl, Stricherl - So wählen Sie richtig
But »Häkchen« sounds so unfriendly and so terribly German ("German" not in the sense of »belonging to the German language« but in the sense of: »belonging to the country Germany«) and therefore we avoid this word too. I think it is because of the uncomfortable combination of k and ch. We never use this word in spoken language and we use it in written texts only if we can't find a better solution. The word Hakerl is much easier to pronounce for Austrian people because we are used to the Austrian diminutive -erl which, on the other hand, seems to be hard to pronounce for some people from Germany.
So, when ever we want to use the German equivalent for the English noun »check« in written texts we get in troubles: Shall we use the very common and familiar but colloquial version »Hakerl« which looks unprofessional in written texts? Or shall we use the inconvenient and offish version »Häkchen« that sounds so terribly Non-Austrian? Both Versions are bad and so many Austrian authors often spend a lot of time thinking over other possibilities.
I'm pretty sure that also in all the editorial offices responsible for the above quotes, there were lengthy discussions before publication about whether or not it was okay to write the word »Hackerl«.
A digression about German diminutive suffixes:
German standard German has only two diminutive suffixes: -chen and -lein (Kindchen, Kindlein; Hündchen, Hündlein). But in Regions where Bavarian or Alemannic dialects are spoken you can hear also some other diminutive suffixes. One of them is -erl (Kinderl, Hunderl) in the region where Bavarian dialects are spoken (which is roughly Bavaria and Austria) which even exists in many words that are part of Austrian standard German (but - as far as I know - do not belong to German standard German or Swiss standard German):
- Schwammerl (Eierschwammerl), Sackerl, Häferl, Schmankerl, Schneckerl, Stockerl, Kipferl, Nockerl, Fleckerl, Busserl, Zuckerl (Eibischzuckerl), Betthupferl, Schöberl, Kracherl, Stüberl (Pressestüberl) ...
The advantage of having an additional option is, that now you can avoid awkward sound-combinations that would appear with the other suffixes. The combination of k followed by ch is such a awkward combination. And this is why in Austria (and probably also in Bavaria) we use other diminutive forms than in other regions. Some of them belong to Austrian Standard German, but most of them belong to colloquial speech:
- Päckchen → Packerl
- Glöckchen → Glockerl, Glöckerl
- Fleckchen → Fleckerl
- Röckchen → Rockerl
- Wölckchen → Wolkerl
- Säckchen → Sackerl
- Schlückchen → Schluckerl
- Häkchen → Hakerl
None of the other diminutive suffixes is part of any of the three standards of German language, they exist only in colloquial speech and in dialects. Some of them are:
- -ele and -ale: Sackele (Sack), Hundale (Hund)
- -li: Säckli (Sack), Hündli (Hund), Röösli (Rose), Chügeli (Kugel)
- -le: Häusle (Haus), Kindle (Kind)