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Short narrated videos and full written lessons on how technology works and how to choose well. Watch the summary in a minute or two; read the lesson for the detail, the sources and the links to rankings.

13 lessons 3 topics 17 minutes of video with captions

How compression works

Run-length encoding, Huffman coding, LZ77 and DEFLATE explained one idea at a time, then how to choose between gzip, xz, Zstandard and Brotli for a real job.

5 lessons

1:24Beginner · 5 min readHow file compression worksSee how lossless compression shrinks files with run-length encoding, Huffman coding and LZ77 pointers, and why ZIP, gzip and PNG all rely on DEFLATE.Watch and read

1:16Beginner · 6 min readHuffman coding explained: shorter codes for common symbolsLearn how Huffman coding builds a tree from symbol counts, gives frequent letters short codes, and decodes without separators, with a worked example.

1:26Intermediate · 6 min readLZ77 and DEFLATE: how ZIP, gzip and PNG compressLearn how LZ77 pointers, DEFLATE blocks and Huffman codes work together, why a pointer can overlap its own output, and how ZIP differs from tar.gz.

1:26Beginner · 7 min readLossless vs lossy compression: what gets thrown awayLossless compression gives back every byte. Lossy compression discards detail on purpose. See what JPEG and MP3 drop, why re-saving hurts, and what to keep.

1:26Intermediate · 6 min readChoosing a compression algorithm: gzip, xz, Zstandard, BrotliCompare gzip, bzip2, xz, Zstandard and Brotli by size, speed and memory, then pick one for web assets, backups, archives or files other people must open.

Choosing software and services

What to keep in mind when comparing products: fair comparisons, the real cost of free, lock-in and exit costs, trials that tell you something, and how to read rankings and reviews.

6 lessons

1:20Beginner · 6 min readHow to compare products fairly: what to keep in mindDefine the job, cap the must-haves, compare like with like, count total cost over one period and weigh the criteria. Includes a worked example.Watch and read

1:25Beginner · 6 min readFree, paid or open source? What each really costsWhat free of charge, free software, open source, freemium and paid mean, the costs that have no price tag, and how to decide by data and time.

1:15Beginner · 5 min readSubscription or one-time purchase: how to chooseCompare what each model pays for, work out the cost over three and five years with example figures, and check the questions to ask before you buy.

1:16Intermediate · 6 min readLock-in and exit costs: check how you leave before you commitLearn what lock-in is, run an export test on real data, compare open formats and local versus hosted storage, and plan an exit with your EU data rights in mind.

1:20Beginner · 5 min readHow to run a software trial that tells you somethingRun a software trial that answers your question. Set criteria first, use real files, test import, export and sharing, then decide before the end date.

1:18Intermediate · 6 min readHow to read rankings and reviews without being misledLearn what a software ranking can show, which parts to read first, how to spot disclosure and dates, and how to read user reviews with care.

Deciding well

How to pick a book worth your time, and how to settle a close call between two good options without losing a week to it.

2 lessons

1:11Beginner · 5 min readHow to pick a book worth your timePick a book by the question it must answer, its level, its edition and a sample chapter, before you buy it or read the reviews.Watch and read

1:17Beginner · 4 min readHow to decide between two good optionsSettle a close call by sorting it by how hard it is to undo, setting a deadline, scoring the criteria as a tie-breaker and writing down why you chose.

From lessons to picks

The lessons teach the thinking behind the rankings. When you are ready to choose, browse the ranked lists by category, set two finalists side by side on the comparison pages, or read how the scores are set in how we rank. Step-by-step buying guides for single categories live on the blog.