Front-end developer and tech writer · View profile
· 14 min read
The extension is almost never the real problem. A .mov and a .mp4 are cousins from the same family of file formats, and what actually stops the video is the codec sealed inside it — usually HEVC. Here is how to tell the two failures apart, and when changing the box is enough.
· 7 min read
You asked for 1:23 and got 1:21. Nothing is broken: a cut that does not re-encode can only land on a keyframe, and how far away the nearest one is depends entirely on what recorded the video. Here is how to know which you have and when to accept the drift.
· 11 min read
A landlord wants page 3. An accountant wants January. You need to send those pages and not the eleven others, and there is a trap: the obvious way leaves the removed pages inside the file you send.
· 8 min read
A duplex scanner that took one side at a time, a stack fed upside down, a page that came out twice. Reordering is not the same operation as extracting pages, and knowing which one you are doing tells you what happens to everything that is not a page.
· 8 min read
You rotated the scan, saved it, and the recipient still opened it sideways. Nothing is broken — rotation in a PDF is an instruction rather than a change to the page, and instructions can be ignored. Here is when that happens and how to produce a file that cannot be misread.
· 11 min read
A character is three different things at once. One emoji with a skin tone is 1 grapheme, 2 code points and 4 UTF-16 units. Every count in this guide was measured in Node, plus why an SMS drops from 160 to 70 and why VARCHAR(255) is not 255 of anything in particular.
· 15 min read
MD5 is broken and MD5 is fine, depending on which of three security properties you needed. Here is what collision resistance, second-preimage resistance and preimage resistance actually mean, which algorithm still has which, and why none of them belongs near a password.
· 9 min read
Nobody owns a scanner any more, so the phone does it. Two things decide whether the result is accepted: how you took the photograph, and what page size it becomes. The second one surprises people, because a photograph turned into a PDF is not A4 unless something makes it A4.
· 11 min read
Flesch Reading Ease and Flesch-Kincaid Grade Level count syllables and sentence length. Nothing else. Both formulas in full, one passage scored end to end, and the comma trick that buys 3.9 grade levels without changing a word.
· 10 min read
A rental file, a loan application, a tender: the requester wants one document, in the order they listed. The merge itself takes seconds. What goes wrong is the ordering, the page sizes and the file that silently loses its signature — all of which are avoidable if you know where they bite.
· 9 min read
Marketplaces, job boards and support forms often accept JPEG and PNG and nothing else. Converting is easy; choosing the resolution is the part that decides whether the recipient can read your document, and it is the part every tool asks you about and nobody explains.
· 10 min read
The first pass takes 30% off and the second takes nothing. That is not a broken tool — it is the difference between removing redundancy and removing information, and knowing which one you are doing tells you when to stop and what a second attempt actually costs.
· 11 min read
The form rejects your file and offers no advice. What works depends entirely on where the megabytes actually are, and for a scanned document the answer is not compression at all — it is resolution. Here is how to tell which case you have in ten seconds.
· 12 min read
Every online file tool promises your document is safe. Almost none tell you whether it leaves your machine at all. There is a five-second test that settles it without reading a single privacy policy, and it works on any tool — including this one.
· 10 min read
The DPI figure inside an image file is a label. It changes no pixels. Printed size is pixels divided by PPI — and DPI, properly used, means something else entirely: the printer's dots.
· 13 min read
A photo file carries coordinates, an exact timestamp, the device and lens, and on some cameras a serial number. Here is what is actually in the block, what stripping does and does not fix, and how to verify it worked.
· 13 min read
Two properties decide the format — photographic or flat-toned, and whether it needs alpha or animation. Everything else is downstream. With measured byte counts for the same two images in all four formats.
· 9 min read
Minute, hour, day of month, month, day of week. The traps are that a step is a stride through a range and not an interval, and that the two day fields are combined with OR — so 0 0 1 * 1 fires on the 1st and on every Monday.
· 9 min read
Four directives, two wildcards, one file at the host root. It is a crawl instruction and nothing more — it does not remove a page from search results, it does not restrict access, and it publishes every path you list in it.
· 7 min read
Nothing is styled. Each letter is swapped for a different Unicode character that happens to look bold or cursive — which is why a screen reader reads the result as gibberish and some devices show empty boxes.
· 8 min read
301 against 308, 302 against 307, 401 against 403, 404 against 410 — plus what Retry-After on a 429 or a 503 actually promises. The pairs where picking the wrong code changes behaviour, not just wording.
· 7 min read
Read is 4, write is 2, execute is 1, and each of the three digits describes a different party. The part most explanations get wrong is what the execute bit does on a directory — it grants traversal, not the right to run anything.
· 4 min read
Every game uses a different sensitivity scale. Convert with the yaw ratio, verify with centimetres per 360 degrees, and keep the muscle memory you spent months building.
· 4 min read
Estimate upload time with one formula: file size in bits divided by your upload speed. Learn why upload is usually slower than download and how overhead affects the result.
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