33 guides on files
Merging, splitting, converting and shrinking documents. These guides say what a conversion actually preserves and what it silently drops, and where a file's limit stops being technical and becomes a legal question about the document itself.
Ranked by how many pages of this site link to them, not by traffic.
Deduplication compares whole rows exactly, cell type included. Five identical-looking rows came out as three, because one held a number, one a string and one a string with a leading space.
Daniel Okonkwo · 4 min read
A spreadsheet file stores both the formula and the last answer Excel computed. Stripping the formula leaves the stored answer — and leaves a blank wherever the file never carried one.
Daniel Okonkwo · 4 min read
One structural difference explains everything else: TAR does not compress, it only stacks; ZIP compresses each file on its own. Measured on 60 small source files, that is the difference between 1,809 bytes and 14,686.
Daniel Okonkwo · 12 min read
Four extensions, three of them the same box with different lids. Rename an XLSX to .zip and it opens — that single fact explains the whole family, and explains why XLS, which does not, is the one still causing trouble.
Daniel Okonkwo · 12 min read
A PDF carries its metadata twice, in two stores that can tell different stories, and neither of them is the whole story. Here is what is actually in the file, what clearing it removes, and the two things that survive every wipe.
Daniel Okonkwo · 15 min read
Numbering a tidy document is trivial. The cases that bite are a page turned sideways, a Letter sheet among A4 ones, a print file with bleed, and a document that already prints its own number. All four were tested: on the first three the number lands exactly where you asked, and the fourth is not detected at all.
Daniel Okonkwo · 14 min read
A PDF stores glyphs at coordinates — not lines, not paragraphs, not a reading order. Extraction rebuilds the text from those positions, which is why two columns come out interleaved, a table loses its cells, and a scan gives you nothing at all. Measured by running the tool.
Daniel Okonkwo · 15 min read
Scaling until the loudest sample hits a ceiling barely changes how loud something sounds. Measuring in LUFS does. This tool measures — in two passes, correctly — and then prints a result it never verified, which on ordinary material can be well over a decibel adrift.
Daniel Okonkwo · 14 min read
One ffmpeg command, no encoder, and a result whose video stream is byte-for-byte the one you started with — verified by checksum. Plus why the file barely shrinks, and the difference between a silent track and no track at all.
Daniel Okonkwo · 11 min read
There are two completely different ways to turn a video, and only one of them touches the picture. This tool takes the slow, lossy, universal road — and there is a good chance your sideways phone clip does not need it at all.
Daniel Okonkwo · 11 min read
Three commands hide behind three buttons: one frame at a timestamp, a fixed number spread across the clip, or one every N seconds. Here are the exact arguments, the 60-frame ceiling and the reason a frame from the middle of a compressed clip can never be as sharp as a keyframe.
Daniel Okonkwo · 12 min read
Whether a drawn signature is valid is settled elsewhere. What decides whether your document actually gets signed is the order you ask people in, what the audit trail records, and six failure modes that have nothing to do with the law.
Daniel Okonkwo · 18 min read
The last resort when nothing can be compressed further. It works, and it has three sharp edges: the parts are useless on their own, the order is absolute, and the megabyte you set is not the megabyte the limit means.
Daniel Okonkwo · 7 min read
Plain text has no layout, so any converter has to invent one for you. Here is exactly which decisions this one makes — page, margins, font, line breaks — what it does with a tab and a long line, and what you have to add yourself before a note is worth keeping.
Daniel Okonkwo · 19 min read
Three completely different faults hide behind the same sentence. One is the encoding, one is the separator, one is Excel guessing at types while it opens the file — and the fix for each is different. Here is how to tell them apart in five seconds.
Daniel Okonkwo · 19 min read
That tick at the edit point is not a flaw in the software. It is a step in the waveform, and a step is broadband energy — which is the definition of a click. Here is the arithmetic, measured, and the two places you can put a cut so it never happens.
Daniel Okonkwo · 18 min read
One of these formats stores the samples, one stores the same samples packed smaller, and one stores a guess about what you would have heard. Which conversions between them are free, which are merely expensive, and which are one-way doors — with the arithmetic for each.
Daniel Okonkwo · 15 min read
The soundtrack inside your video has already been through a lossy encoder once. Whether extracting it costs you a second pass depends entirely on which of the three buttons you press — and "extract to MP3", the one everybody reaches for, is the one that costs.
Daniel Okonkwo · 15 min read
A GIF has no real video compression: every frame is a whole picture, capped at 256 colours. That gives you an arithmetic you can do in your head — width times height times frames — and three levers to pull when the upload box says the file is too big.
Daniel Okonkwo · 14 min read
Going from 1080p to 720p does not halve the picture: it removes 56 % of the pixels, and it removes rather less than that of the file. Here is the ladder with real pixel counts, honest bitrates and what three minutes weighs at each rung — plus the reason a low-bitrate source barely shrinks at all.
Daniel Okonkwo · 11 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.
Daniel Okonkwo · 14 min read
The quality slider cannot aim at a file size — that is not what it is for. But the limit and the length of your clip already fix the bitrate you are allowed to spend, and one division tells you whether the resolution you are using can possibly fit.
Daniel Okonkwo · 14 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.
Daniel Okonkwo · 7 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.
Daniel Okonkwo · 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.
Daniel Okonkwo · 8 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.
Daniel Okonkwo · 11 min read
Drawing your name onto a PDF produces a simple electronic signature. European law says that cannot be dismissed just for being electronic — and also that it carries none of the presumptions a qualified signature does. Knowing which tier you have is the difference between a document that holds and one you have to defend.
Camille Laurent · 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.
Daniel Okonkwo · 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.
Daniel Okonkwo · 9 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.
Daniel Okonkwo · 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.
Daniel Okonkwo · 10 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.
Daniel Okonkwo · 11 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.
Daniel Okonkwo · 12 min read