Guides

Why PDFs get big, and how to get one under an email or upload limit.

• How to Compress a PDF to 100 KB, 200 KB, or 1 MB

  Upload forms don't negotiate: under the limit or rejected. Here's what each size target realistically takes, and the honest truth about when a target isn't reachable.

• How to Get a PDF Under an Email Attachment Limit

  Your email bounced, the file is 24 MB, and the limit says 25 MB. That isn't a mistake: attachments get bigger in transit, and almost nobody tells you by how much. Here's the real number to aim for, and what each provider actually allows.

• Why Is My PDF So Large?

  Twenty-two pages of plain text, and the file is 24 MB. Nothing on the page explains it. There is one test that identifies the cause in about ten seconds, and for most oversized PDFs the answer is the same.

Building, combining, and trimming documents, from photos to a finished PDF.

• How to Merge PDF Files (and Keep Them in Order)

  One attachment beats five. Merging PDFs takes under a minute. The part worth thinking about is order, and what to do when the combined file gets big.

• How to Delete or Remove Pages from a PDF

  PDFs don't have a delete key, but they don't need one. Whether you'd call it deleting, removing, cutting out or taking out pages, the move is the same: name the pages you want to keep, and what's left behind is gone. Here are the recipes.

• PDF to PNG or JPG: Which Should You Export?

  Both tools turn PDF pages into images, and the right one depends entirely on what's printed on the page. The size penalty for choosing PNG is far smaller than most people expect on text, and far larger than they expect on photos.

What HEIC is, why other devices struggle with it, and how to get usable photos.

• What Is a HEIC File? Apple's Photo Format, Explained

  If you've plugged an iPhone into a Windows PC and found photos that won't open, you've met HEIC. Here's what the format is, why Apple chose it, and your options for dealing with it.

• HEIC vs JPG: Which Should Your Photos Use?

  HEIC gives you double the photos per gigabyte; JPG gives you a file that opens on anything made in the last thirty years. Here's how to decide which trade-off is yours.

• How to Open HEIC Files on Windows

  The standard advice is one line: install HEIF Image Extensions from the Microsoft Store. For a lot of people that works. For a lot of others the photo still won't open afterwards, and almost nobody explains why. Here is the whole picture, including the case where the answer is that you can't.

PNG, JPG, WebP: what each is good at, and which one your job needs.

• PNG vs JPG: Which Image Format Should You Use?

  PNG and JPG solve different problems. Pick the wrong one and you get either a blurry logo or a 8 MB photo that email refuses to send. Here's the whole decision in a few minutes.

• PNG vs WebP: What's the Difference?

  WebP does most of what PNG does at a fraction of the size, which is why performance audits keep telling you to switch. Here's what actually changes, and when PNG is still the right answer.

• JPG vs WebP: Which Is Better?

  For photos on the web, WebP is simply the better JPG: same picture, quarter to a third fewer bytes. Off the web, the answer flips. This guide draws the line.

• WebP Files Won't Open? Why It Happens and How to Fix It

  You right-clicked an image, saved it, and now Word, Photoshop, or an upload form refuses to touch it. The file is almost certainly a WebP, or, increasingly, an AVIF. Neither is broken; they're just newer than the software you're trying to use.

Reading the errors your tools throw, and what a validator can't tell you.

• Why Is My JSON Invalid?

  A parser rejected your JSON and handed you something like “Expected double-quoted property name at position 7”. That names the place, not the cause. Here is what it is almost always telling you.

What a SKILL.md is, how Claude finds and loads it, the format field by field, and how to write one that triggers when it should.

• How to Create a Claude Skill

  A Claude skill is a folder holding a SKILL.md file that teaches Claude a task you keep repeating. To create a Claude skill you need no code: a folder, a short file with two required fields, and a test. This guide covers the five steps, with the rules from the published format, and points to the deeper guides where a step needs one.

• How to Write a SKILL.md File

  Writing a SKILL.md file is mostly a writing problem, not a formatting one. The format is two required fields and some Markdown. What decides whether Claude uses the skill is the description, and what decides whether the result is any good is how the instructions are written. This guide covers both, using the rules in Anthropic's authoring guide and the Agent Skills specification.

• Claude SKILL.md Format Explained

  The SKILL.md format has two parts: YAML frontmatter that tells Claude when to use the skill, and a Markdown body that tells it how. Two fields are required, four more are in the open specification, and Claude Code understands a further set that no other surface accepts. This page lists every field with its limits, as published in the Agent Skills specification and Anthropic's documentation.

• How to Build a Claude Code Skill

  A Claude Code skill is a SKILL.md file in a folder that Claude Code watches. That much is shared with every other surface. What is specific to Claude Code is where it looks, how a skill becomes a slash command with arguments, and the frontmatter that controls who can invoke it and which tools it may use without asking. This guide covers those parts, as documented in the Claude Code skills reference.

• Claude Skills vs MCP

  Claude Skills and MCP get compared because both extend what Claude can do, but they extend different things. A skill changes what Claude knows: it is a folder of instructions loaded when a task matches. MCP, the Model Context Protocol, changes what Claude can reach: it is an open standard for connecting to outside tools and data through servers. Most real setups use both, and this guide explains where the line falls.

• How to Install a Claude Skill

  Installing a Claude skill means putting a folder where the product you use looks for it. There are three products with three different answers, and skills do not sync between them. This guide gives the exact location for each, what to check before installing a skill someone else wrote, and why a skill sometimes fails to appear.

• How to Structure a SKILL.md File

  The structure of a SKILL.md file follows one idea: Claude should load as little as possible until it needs more. The specification calls this progressive disclosure, and it shapes everything from the order of sections to which files sit next to SKILL.md in the folder. This guide gives a section order that works, the folder layout, and the rules for splitting a skill that has grown.

Removing and blurring backgrounds, hiding faces, and upscaling: what the models can do, where they fail, and how to get a clean result.

• Which Photos Work with a Background Remover

  Automatic background removal is excellent on some photos and hopeless on others, and which one you have is predictable before you start. Here is what the model is reliable at, what defeats it, and what to do when the edge comes back rough instead of clean.

• How to Make an Image Background Transparent

  A transparent background lets an image sit on anything (a coloured slide, a website, a T-shirt mock-up) without a white box around it. Getting one is a two-part problem: separating the subject, and saving in a format that can hold transparency. Most failures are the second part.

• How to Upscale an Image Without Losing Quality

  "Without losing quality" is the phrase everyone searches and no tool can literally promise. Enlarging an image means inventing pixels that weren't there. The question is whether the invented pixels look right, and modern super-resolution models are genuinely good at that, within limits worth knowing before you start.

• How to Increase Image Resolution

  A form rejects your photo for "low resolution". A printer says 300 DPI. A website wants 1200 pixels wide. These sound like the same problem and they are not. Sorting out which one you have is most of the work.

• How to Blur the Background of a Photo

  A blurred background does two things at once: it makes the subject stand out, and it hides whatever was behind them: the messy desk, the other people, the screen you'd rather not show. Phones fake it with a depth sensor. In a browser, a model finds the subject and does the rest.

• How to Blur Faces in a Photo Before Sharing It

  The photo is good and you want to post it. It also has your kid's classmates in it, or colleagues who didn't sign up to be on your feed, or a stranger who happened to be in frame. Blurring their faces lets you share the moment without publishing their identities. Here is how to do it properly, including the part where you check the tool's work.