user3594: I am looking for a relatively large PGN-formatted database (with at least 500k+ games), that is downloadable, with possibly the following properties:

Simple formatted (no time indication after moves, etc), i.e. game info headers on top, followed by the moves, an example: (it doesn't have to contain all the headers of this example) 
Few such, but very small (2-3 thousand games) databases can be found here.
It would be preferential if the database was diverse, for example not being only composed of man vs. machine games or somesuch. No real constraint on the ratings, whether the levels (amateur to super grandmaster) are fairly balanced or whether it's a 2000+ rating database.
Although a single-file database would be easiest to work with, say for parsing purposes, one that is divided onto multiple PGN files would also be perfectly fine, as long as they were formatted similarly and did not contain too many duplicates.

In other posts, one mentioned database with similar properties to the above is the ICOFY database, but unfortunately it does not seem to be maintained any longer, nor can a trustworthy download link for it be found. 

user4543: Here! Indexed by openings ECO code. http://www.logicalchess.com/learn/lessons/openings/pgndb/index.html. 

user19786: There are a lot of PGN file database download sites, the best and most comprehensive one is probably PGN Mentor at https://www.pgnmentor.com/files.html
They have several databases containing thousands of games that can be downloaded and easily merged into a single DB using a command window
But very few of these games are annotated, so I have put about 950 annotated games, which are in 9 separate ".pgn" files, here 
Annotated PGN file download page

user4509: Do not know if it really suits you but on http://www.theweekinchess.com/twic you can download a lot of PGN files. I once saw an explanation how somebody used this to create an opening book out of it. I could not find one big file with all games but there are quite a lot of files that date back to 25/06/2012. You can always make 1 big file out of it.

3594: <p>I am looking for a relatively large PGN-formatted database (with at least 500k+ games), that is downloadable, with possibly the following properties:</p>

<ul>
<li><p>Simple formatted (no time indication after moves, etc), i.e. game info headers on top, followed by the moves, an example: <em>(it doesn't have to contain all the headers of this example)</em>  <a href="https://i.stack.imgur.com/v0WsW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/v0WsW.png" alt="enter image description here"></a></p></li>
<li><p>Few such, but very small (2-3 thousand games) databases can be found <a href="http://chessproblem.my-free-games.com/chess/games/Download-PGN.php" rel="nofollow noreferrer">here</a>.</p></li>
<li><p>It would be preferential if the database was diverse, for example not being only composed of man vs. machine games or somesuch. No real constraint on the ratings, whether the levels (amateur to super grandmaster) are fairly balanced or whether it's a 2000+ rating database.</p></li>
<li><p>Although a single-file database would be easiest to work with, say for parsing purposes, one that is divided onto multiple PGN files would also be perfectly fine, as long as they were formatted similarly and did not contain too many duplicates.</p></li>
</ul>

<p>In other posts, one mentioned database with similar properties to the above is the ICOFY database, but unfortunately it does not seem to be maintained any longer, nor can a trustworthy download link for it be found. </p>
 4543: <p>Here! Indexed by openings ECO code. <a href="http://www.logicalchess.com/learn/lessons/openings/pgndb/index.html" rel="nofollow">http://www.logicalchess.com/learn/lessons/openings/pgndb/index.html</a>. </p>
 19786: <p>There are a lot of PGN file database download sites, the best and most comprehensive one is probably PGN Mentor at <a href="https://www.pgnmentor.com/files.html" rel="nofollow noreferrer">https://www.pgnmentor.com/files.html</a></p>

<p>They have several databases containing thousands of games that can be downloaded and easily merged into a single DB using a command window</p>

<p>But very few of these games are annotated, so I have put about 950 annotated games, which are in 9 separate ".pgn" files, here </p>

<p><a href="https://pgnchessbook.org/pgn/" rel="nofollow noreferrer">Annotated PGN file download page</a></p>
 4509: <p>Do not know if it really suits you but on <a href="http://www.theweekinchess.com/twic" rel="nofollow">http://www.theweekinchess.com/twic</a> you can download a lot of PGN files. I once saw an explanation how somebody used this to create an opening book out of it. I could not find one big file with all games but there are quite a lot of files that date back to 25/06/2012. You can always make 1 big file out of it.</p>
