Guides
Short, practical guides about file formats and conversion tasks. Each one answers a real question and links to the tool that does the job.
What does 300 DPI mean?Tie DPI to pixels with one formula and a worked print exampleHow many words is 3000 characters, and how do you plan around it?Turning a character limit into a word target and planning an essay or application around itCombining separate PDFs into a single filePutting separate PDFs into one application file, in the right orderWhat do %20, %C3%A9 and similar codes in a link mean?How to read the percent codes in a link and share it without breaking itWhat is Base64, and why is that wall of random text there?How to recognise a Base64 string, turn it back into a file, or send oneCombining several photos into one PDFCollect many images into a single document ready to printWhat is the difference between CSV and XLSX?How the two table formats differ, upload screens, and switching safelyWhat is a CSV file, and why do special characters break in Excel?Why accented characters garble in CSV files, and how to fix itWhat is a file extension?What the label after the dot is, and why it does not define the fileBright on screen, dull on paper: CMYK vs RGBWhy printed colour drifts, the limit of formula conversion and how to talk to the print shopWhat is an EML file, how do you open it, and how do you turn it into a PDF?Opening an .eml you were sent, and turning an email into a PDF recordHow do you open an EPUB file, and what changes in a PDF?How to open a downloaded .epub on each device, and when converting it to PDF makes senseHow do you get a contact list from Excel into your phone?Adding hundreds of numbers from a spreadsheet to your phone's contacts in one goWhat is a favicon, and which sizes do you need?Where the tab icon shows up and which sizes it has to coverReducing a photo's file sizeTwo separate ways to get a file under a KB limitWhy does my photo turn sideways on the computer or when uploaded?The real reason a photo opens sideways, and the fix that makes it upright everywhereHow to add a watermark to a photo, from ID copies to product shotsPutting the right words in the right place on an ID copy or a sales photoPutting a photo on a white backgroundFilling an empty background versus erasing a real oneRemoving location and EXIF data from photosWhere the hidden location record lives, which channels strip it, and how to verifyGIF too big to upload: how do you make it smaller?Getting an oversized GIF under the limit with frames, size and colourHow to create a strong passwordWhy length beats complexity, the random-word method, and a six-question checkWhat is a hex colour code, and how do you read #2F6FED?What the six characters mean, and how to find a colour's codeHow to put two photos side by side in one pictureTurning a before-and-after pair or two documents into one pictureHow do you find the differences between two texts?Finding what changed between two versions of a document, by the right route and without the usual trapsIs your download corrupted or tampered with? Check it with SHA-256How to compare your file with the SHA-256 value printed on the download pageInstagram and social media image sizesRatios are the lasting part; pixel figures come secondWhat is JSON, and how do you read a .json file?Opening, reading and converting a .json file, in plain languageWhat is lorem ipsum, and where does it come from?Where the Latin-looking filler comes from, what it is for, and how to clear it before publishingWhat is Markdown, and how do you read a .md file?What the Markdown marks mean and what to do with a .md fileHow many characters fit where?Common platform limits, the SMS encoding trap, and how to count what you wroteWhat is an ODT file, and how do you turn it into a PDF?Three ways to open an .odt you were sent and turn it into a PDF, depending on the software you haveHow to reduce a PDF's file size, and what you give upGetting a 9 MB PDF under a 2 MB upload limit, and knowing the costYour PDF asks for a password every time: removing it for goodTurning your own password-protected document into a copy that stops asking, when you know the passwordPrinting a PDF in black and white: printer setting or converted file?Choosing between a grayscale print setting and a converted PDFWhy does converting a PDF to Word break the layout?What to expect when tables scatter or fonts change after a conversion, and what to do about itHiding an ID number, address or bank details in a PDF: why a black box is not enoughWhy text survives under a black box, how to remove it for real, and how to check before you sendPNG or JPG? Which one, and whenChoosing the right format for photos, screenshots and logosWhat is a RAW file, and why won't my CR2 or NEF photos open?Recognising, opening and converting the RAW files your camera producedWhat is SVG, and when do you convert it to PNG?How a vector file works and when a PNG export becomes necessaryYour spreadsheet shows 1728734400 where a date should be?How to turn 10 and 13-digit numbers in a spreadsheet into your local timeWhat is a scanned PDF, and why can't I select the text?If the text in a PDF won't select or search, the page is a photo; how to tell and what to doTurning a phone photo into a PDFConvert a document photo to PDF without a computerWhat is a TIFF file, and how do you open a scanned .tif?What to do with a .tif that is huge, won't open or shows only one pageHow to create a QR code for freeStatic versus dynamic codes, the right print size, and testing before you printWhat are UTM codes, and what does ?utm_source in a link mean?What the tags at the end of a link mean, a naming scheme for a small business, and where they show up in reportsPassport and ID photo sizesWhich country asks for which size, and what it is in pixelsWhat is WebP, and why won't it open?What to do when a saved picture arrives as .webp, and when to convertHow do you create a WhatsApp link, and where should it go?Setting up the WhatsApp link for your Instagram bio and business card properlyWhat is the difference between XML and JSON?How the two data formats differ, how to tell them apart, what converting changesHow do you open a ZIP file, and why won't the files inside open?Extracting a .zip you were sent, and telling locked, garbled and RAR archives apart