Choosing the best online CSS compression service

Currently, there are a huge number of web tools for optimizing CSS files. Most of them have their own algorithm of work (there are, of course, duplicates). The effectiveness of the programs themselves is also significantly different. In addition, some optimizers can “break” CSS code, after which styles become invalid. As practice shows, the percentage of such "useful" tools is quite high.

This article is a test report of the most popular online optimizers. The experiment was conducted on 3 CSS files. Links to each of them are given in the results table.

The main goal of the work is a comparative characteristic of services in terms of the main indicator (degree of compression). The presence of various settings, usability and other minor factors were not taken into account.
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It is worth saying that 6 out of 17 optimizers reviewed did not cope with the task. Results that have not been validated after compression are marked with a dash.

CSS file link	www.kartinki24.ru/templates/kartinki/style/styles.css	gidonline.club/wp-content/themes/gidonline/style25.css	spb.azbyka.net/views/azbyka/css/style.css	Wed result after compression,%
Original size, KB	21.49	26.20	23,18
Service	Results, KB
askapache.com/online-tools/compress-css	18.55	24.23	23,17	93.06
cleancss.com/css-minify	18.01	23.67	22.38	90.39
codebeautifier.com	-	-	-	-
creativyst.com/Prod/3	20.58	-	23,18	-
css-school.ru/optimiser	16.95	23.00	-	-
csscompressor.com	17.77	23.46	22.32	89.67
cssdrive.com/index.php/main/csscompressor	18.02	23.66	22.37	90.38
cssportal.com/css-optimize	19.29	26.20	23,18	96.9
cssresizer.com	17.07	20.20	22.35	84.13
cy-pr.com/tools/css	16.79	22.98	-	-
iceyboard.no-ip.org/projects/css_compressor	-	22.75	-	-
lotterypost.com/css-compress.aspx	17.78	23.43	22.31	89.63
pagecolumn.com/tool/css_compressor.htm	18.07	23.66	-	-
partnerki-runeta.ru/css-optimized	18.09	23.67	22.38	90.5
phpinsider.com/compress_css.php	19.29	25.44	22.38	94.69
prohtml.net/services/css-min	18.36	24.27	22.37	91.72
refresh-sf.com	16.87	21.18	22.19	85

As we see, it is impossible to single out the leader unequivocally. In each of the 3 tests, the minimum size was achieved using different services. However, if we consider the average result, then 2 tools stand out with a sufficiently large margin:

1. cssresizer.com (84.13%);
2. refresh-sf.com (85%).

The bronze medalist was csscompressor.com , with the result (89.67%). The rest of the programs were able to reduce the size of styles by no more than 10%.