Utilumo Learn

What is EXIF metadata?

Thu, 25 Jun 2026 00:00:00 GMT

EXIF is the hidden metadata cameras and phones write into photos, including GPS location, device model, and timestamps. Here is what it stores and how to remove it.

How to compress images for the web

Thu, 25 Jun 2026 00:00:00 GMT

A practical guide to making images smaller without obvious quality loss: choosing lossy vs lossless, resizing first, picking a format, and tuning quality.

PNG vs JPG: which should you use?

Thu, 25 Jun 2026 00:00:00 GMT

PNG is lossless with transparency, ideal for graphics and screenshots. JPG is lossy and smaller, ideal for photos. Here is how to choose.

WebP vs AVIF: which modern image format wins?

Thu, 25 Jun 2026 00:00:00 GMT

AVIF usually compresses smaller and supports HDR, while WebP encodes faster and has slightly broader support. Here is how to choose between them.

What is SVG?

Mon, 29 Jun 2026 00:00:00 GMT

SVG is a vector image format written as text, so it scales to any size without blurring. Here is how it differs from PNG and JPG and when to use it.

HEX, RGB, and HSL color codes explained

Mon, 29 Jun 2026 00:00:00 GMT

HEX, RGB, and HSL are three ways to write the same color. Here is what each means, how they relate, and when each is easiest to use.

What is DPI and image resolution?

Mon, 29 Jun 2026 00:00:00 GMT

Resolution is how many pixels an image has; DPI is how densely they print. Here is how the two relate and why DPI rarely matters on screen.

How to crop, rotate, and flip images

Mon, 29 Jun 2026 00:00:00 GMT

Cropping, rotating, and flipping are the basic image edits. Here is what each one does, when to use it, and how to keep the work local.

What is an alpha channel (image transparency)?

Mon, 29 Jun 2026 00:00:00 GMT

The alpha channel stores how transparent each pixel is, letting images have see-through areas. Here is how it works and which formats support it.

How to convert PNG to JPG

Wed, 01 Jul 2026 00:00:00 GMT

Convert a PNG to JPG in your browser to shrink photo file sizes. Learn when to convert, what happens to transparency, and how to keep quality high.

How to resize an image without losing quality

Wed, 01 Jul 2026 00:00:00 GMT

Resize a photo to specific pixel dimensions in the browser. Learn the difference between fit and exact resizing, and how to avoid a blurry result.

JPG vs WebP: which should you use?

Wed, 01 Jul 2026 00:00:00 GMT

WebP produces smaller files than JPG at similar quality and supports transparency. Here is when WebP wins, when JPG is safer, and how to convert.

How to convert JPG to PNG

Wed, 01 Jul 2026 00:00:00 GMT

Convert a JPG to PNG in your browser when you need lossless quality or transparency. Learn what conversion can and cannot restore.

How to remove EXIF data from photos

Wed, 01 Jul 2026 00:00:00 GMT

Strip EXIF metadata — including GPS location — from your photos in the browser before sharing them. Learn what EXIF exposes and how to remove it.

How to compare two images

Thu, 02 Jul 2026 00:00:00 GMT

Spot the exact pixel differences between two images in your browser. Learn when a visual diff helps and how to read the highlighted result.

How to convert an image to ASCII art

Wed, 08 Jul 2026 00:00:00 GMT

Turn a photo or logo into text-based ASCII art in your browser. Learn how the conversion works and how to get a clean, recognizable result.

What is JSON?

Thu, 25 Jun 2026 00:00:00 GMT

JSON is a lightweight, text-based format for storing and exchanging structured data. Here is how it works, its data types, and the rules that trip people up.

What is Base64 encoding?

Thu, 25 Jun 2026 00:00:00 GMT

Base64 encodes binary data into plain ASCII text so it can travel safely through systems built for text. It is encoding, not encryption.

JWT explained: how JSON Web Tokens work

Thu, 25 Jun 2026 00:00:00 GMT

A JWT is a signed, Base64url-encoded token with three parts: header, payload, and signature. Here is what each part holds and why decoding is not verifying.

What is a UUID?

Thu, 25 Jun 2026 00:00:00 GMT

A UUID is a 128-bit identifier that is unique without a central authority. Here is how UUID v4 works, why collisions are effectively impossible, and when to use it.

Cron syntax explained with examples

Thu, 25 Jun 2026 00:00:00 GMT

Cron schedules use five fields: minute, hour, day of month, month, and day of week. Here is what each field means, the special characters, and ready-to-use examples.

How to convert CSV to JSON

Thu, 25 Jun 2026 00:00:00 GMT

Turn spreadsheet-style CSV rows into an array of JSON objects: how the header row becomes keys, how to handle quotes and commas, and common pitfalls.

What are HTTP security headers?

Mon, 29 Jun 2026 00:00:00 GMT

HTTP security headers tell browsers how to handle scripts, frames, referrers, permissions, and HTTPS. Learn the core headers and how to test them safely.

What is hexadecimal?

Thu, 25 Jun 2026 00:00:00 GMT

Hexadecimal is base 16, a compact way to write binary. Here is how hex maps to bits and bytes, why colors and memory use it, and how to convert it.

Regular expressions explained

Mon, 29 Jun 2026 00:00:00 GMT

A regular expression is a pattern that matches text. Here are the core building blocks — character classes, quantifiers, anchors, and groups — with examples.

YAML vs JSON: when to use each

Mon, 29 Jun 2026 00:00:00 GMT

YAML is easier for humans to write and supports comments; JSON is stricter and universal for APIs. Here is how they differ and how to convert between them.

What is a Unix timestamp?

Mon, 29 Jun 2026 00:00:00 GMT

A Unix timestamp counts the seconds since 1 January 1970 UTC. Here is why systems use it, how to read it, and the 2038 limit to know about.

What is a hash function?

Mon, 29 Jun 2026 00:00:00 GMT

A hash function turns any input into a fixed-length fingerprint. Here is what makes a good one, why hashing is not encryption, and where SHA-256 fits.

Markdown vs HTML: when to use each

Mon, 29 Jun 2026 00:00:00 GMT

Markdown is a simple way to write formatted text; HTML is the markup browsers render. Here is how they relate and when to reach for each.

What are HTML entities?

Mon, 29 Jun 2026 00:00:00 GMT

HTML entities are codes that represent characters which would otherwise break markup or cannot be typed, like < for < and & for &.

What is a REST API?

Tue, 07 Jul 2026 00:00:00 GMT

A REST API lets programs talk over HTTP using URLs, methods, and status codes. Here are the core ideas: resources, verbs, and stateless requests.

JSON vs XML: which data format to use

Mon, 29 Jun 2026 00:00:00 GMT

JSON is compact and dominant for web APIs; XML is verbose but supports attributes, namespaces, and schemas. Here is how they differ and when each fits.

What is JSON Schema?

Mon, 29 Jun 2026 00:00:00 GMT

JSON Schema is a JSON document that describes the shape of other JSON: required fields, types, and constraints. Here is how it works and why it is useful.

How to generate TypeScript types from JSON

Mon, 29 Jun 2026 00:00:00 GMT

Turn a sample JSON response into TypeScript interfaces so your code is type-checked. Here is the workflow and the gaps to fix by hand.

What is cURL?

Tue, 07 Jul 2026 00:00:00 GMT

cURL is a command-line tool for sending HTTP requests. Here is how to read a curl command, the flags you will see most, and why it is everywhere.

What is a Content Security Policy (CSP)?

Mon, 29 Jun 2026 00:00:00 GMT

A Content Security Policy tells the browser which sources of scripts, styles, and other content to trust. Here are the key directives and how to roll one out safely.

What is a security.txt file?

Mon, 29 Jun 2026 00:00:00 GMT

security.txt is a standard file that tells security researchers how to report a vulnerability to you. Here is where it goes and which fields it uses.

What is an HTTP header?

Mon, 29 Jun 2026 00:00:00 GMT

HTTP headers carry metadata about a request or response: content type, caching, authentication, and more. Here are the ones you will meet most.

How to convert JSON to CSV

Mon, 29 Jun 2026 00:00:00 GMT

Turning JSON into CSV flattens an array of objects into a table. Here is how keys become columns and how to handle nested data.

What is the CSS box model?

Mon, 29 Jun 2026 00:00:00 GMT

Every element is a box made of content, padding, border, and margin. Here is how those layers work and why box-sizing matters.

What is Markdown?

Mon, 29 Jun 2026 00:00:00 GMT

Markdown is a lightweight way to write formatted text using plain characters. Here is what it is, why it is popular, and where it is used.

What is CSV?

Mon, 29 Jun 2026 00:00:00 GMT

CSV is a plain-text format for tables: one row per line, values separated by commas. Here is how it works and the quoting rules that trip people up.

What is XML?

Mon, 29 Jun 2026 00:00:00 GMT

XML is a markup language for structured data using nested tags and attributes. Here is how it works and where it is still widely used.

How to format (pretty-print) JSON

Wed, 01 Jul 2026 00:00:00 GMT

Format messy or minified JSON into clean, indented, readable output. Learn what pretty-printing does, how to validate, and how to minify again.

What is an API?

Wed, 01 Jul 2026 00:00:00 GMT

An API is a contract that lets one program request data or actions from another. Here is what an API is, how web APIs work, and the terms you will meet.

How to decode Base64

Wed, 01 Jul 2026 00:00:00 GMT

Decode a Base64 string back to text or a file in your browser. Learn how to spot Base64, handle URL-safe variants, and avoid corrupting binary data.

What is a webhook?

Wed, 01 Jul 2026 00:00:00 GMT

A webhook is a reverse API call: instead of you polling for data, a server sends an HTTP request to your URL when an event happens. Here is how they work.

How to generate a hash (MD5, SHA-256)

Wed, 01 Jul 2026 00:00:00 GMT

Generate an MD5, SHA-1, or SHA-256 hash of text in your browser. Learn what a hash is for, which algorithm to pick, and why hashing is one-way.

What is a cron job?

Wed, 01 Jul 2026 00:00:00 GMT

A cron job is a task scheduled to run automatically at set times on a server. Here is what cron is, how the schedule syntax works, and common examples.

How to generate a UUID

Wed, 01 Jul 2026 00:00:00 GMT

Generate a UUID (v4 random or v7 time-ordered) in your browser. Learn which version to pick, what a UUID looks like, and when to use one.

What is YAML?

Wed, 01 Jul 2026 00:00:00 GMT

YAML is a human-friendly data format used for configuration files. Here is how its indentation-based syntax works and how it compares to JSON.

What is a MIME type?

Wed, 01 Jul 2026 00:00:00 GMT

A MIME type tells software what kind of file it is dealing with, like text/html or image/png. Here is how they are structured and where they are used.

How to test a regular expression

Wed, 01 Jul 2026 00:00:00 GMT

Test a regex against sample text to see what it matches before using it in code. Learn a safe workflow, flags, and how to debug a pattern that fails.

How to format (beautify) SQL

Wed, 01 Jul 2026 00:00:00 GMT

Format messy or minified SQL into readable, indented queries. Learn what a formatter does, why it helps reviews, and how to keep keywords consistent.

HTTP status codes explained

Wed, 01 Jul 2026 00:00:00 GMT

HTTP status codes tell you the result of a request — 200 OK, 301 redirect, 404 not found, 500 error. Here is what each group means and the common codes.

What is a SQL JOIN?

Thu, 02 Jul 2026 00:00:00 GMT

A SQL JOIN combines rows from two tables based on a related column. Here are the join types — INNER, LEFT, RIGHT, FULL, CROSS — and when to use each.

How to write a SQL query

Thu, 02 Jul 2026 00:00:00 GMT

Write a SQL SELECT query step by step — choosing columns, filtering with WHERE, sorting, grouping, and joining tables. With a runnable example.

What is SQLite?

Thu, 02 Jul 2026 00:00:00 GMT

SQLite is a small, self-contained SQL database engine that stores a whole database in a single file. Here is what makes it different and where it shines.

What is Permissions-Policy?

Thu, 02 Jul 2026 00:00:00 GMT

Permissions-Policy is an HTTP header that controls which browser features a site and its iframes may use, like camera, microphone, and geolocation.

How to convert HTML to Markdown

Wed, 08 Jul 2026 00:00:00 GMT

Turn HTML from a web page, email, or AI output into clean Markdown in your browser. Learn what converts cleanly and what to check afterward.

camelCase vs snake_case vs kebab-case

Thu, 25 Jun 2026 00:00:00 GMT

A quick reference to the common programming naming styles, where each one is conventional, and how to convert text between them.

How is reading time calculated?

Thu, 25 Jun 2026 00:00:00 GMT

Reading time is an estimate based on word count and an average reading speed. Here is the formula, the typical speeds used, and why it is only an estimate.

What is a URL slug?

Mon, 29 Jun 2026 00:00:00 GMT

A URL slug is the readable, hyphenated part of a web address that names a page. Here is what makes a good slug and how to create one from a title.

How to remove duplicate lines from text

Mon, 29 Jun 2026 00:00:00 GMT

Removing duplicate lines cleans up lists, logs, and exports. Here is how deduplication works and the choices that change the result.

What is UTF-8?

Mon, 29 Jun 2026 00:00:00 GMT

UTF-8 is the encoding that lets text store any character, from ASCII to emoji, as bytes. Here is how it works and why it is the web's default.

Title case vs sentence case

Wed, 01 Jul 2026 00:00:00 GMT

Title case capitalizes the main words; sentence case capitalizes only the first word. Here is when to use each and how to convert text between them.

Common aspect ratios explained

Thu, 25 Jun 2026 00:00:00 GMT

An aspect ratio is the proportion of width to height. Here is what 16:9, 4:3, 1:1, and 9:16 mean and where each is used.

How to calculate percentage change

Thu, 25 Jun 2026 00:00:00 GMT

Percentage change measures how much a value grew or shrank relative to its starting point. Here is the formula, worked examples, and the mistakes to avoid.

What is color contrast (and the WCAG ratios)?

Mon, 29 Jun 2026 00:00:00 GMT

Color contrast is the difference in brightness between text and its background. Here are the WCAG ratio thresholds that keep text readable for everyone.

What is UTC, and how do time zones work?

Mon, 29 Jun 2026 00:00:00 GMT

UTC is the global time reference that every time zone is defined against. Here is how offsets work, why UTC is not the same as GMT in practice, and why DST complicates things.

Metric vs imperial units explained

Mon, 29 Jun 2026 00:00:00 GMT

Metric and imperial are the two main systems of measurement. Here is how they differ, the most useful conversions, and why precision matters.

How to calculate a percentage

Wed, 01 Jul 2026 00:00:00 GMT

Work out a percentage of a number, what percent one number is of another, and percentage increase or decrease — with simple formulas and examples.

How to calculate aspect ratio

Wed, 01 Jul 2026 00:00:00 GMT

Work out the aspect ratio of any width and height, and resize while keeping proportions. Learn the simple method and common ratios like 16:9.

How to convert Celsius to Fahrenheit

Wed, 01 Jul 2026 00:00:00 GMT

Convert Celsius to Fahrenheit with the simple formula, a quick mental shortcut, and a reference of common temperatures.

How to convert between time zones

Wed, 01 Jul 2026 00:00:00 GMT

Convert a time from one time zone to another without mistakes. Learn to work through UTC, handle daylight saving, and schedule across regions.

How to calculate BMI

Wed, 08 Jul 2026 00:00:00 GMT

Calculate your Body Mass Index (BMI) with the metric and imperial formulas, see the standard categories, and understand what BMI can and cannot tell you.

How to calculate your exact age

Wed, 08 Jul 2026 00:00:00 GMT

Work out your exact age in years, months, and days from a birth date. Learn the method, why leap years matter, and how to count age between any two dates.

How to calculate a tip

Wed, 08 Jul 2026 00:00:00 GMT

Work out a tip and split the bill in seconds. Learn the simple percentage method, common tip rates, and how to divide the total between people.

The anatomy of a URL

Thu, 25 Jun 2026 00:00:00 GMT

Every URL is made of parts: scheme, host, port, path, query, and fragment. Here is what each piece does, with a labelled example.

What is URL encoding (percent-encoding)?

Thu, 25 Jun 2026 00:00:00 GMT

URL encoding replaces unsafe characters with a percent sign and a hex code so they can travel safely inside a URL. Here is how and when it happens.

What are UTM parameters?

Mon, 29 Jun 2026 00:00:00 GMT

UTM parameters are tags added to a URL so analytics can tell where traffic came from. Here are the five parameters and how to use them consistently.

How to remove tracking parameters from URLs

Mon, 29 Jun 2026 00:00:00 GMT

Long links are often full of tracking tags like utm_ and fbclid. Here is what they are, why to strip them, and how to share clean URLs.

How to build a query string

Mon, 29 Jun 2026 00:00:00 GMT

A query string passes parameters in a URL. Here is how to format key/value pairs, encode values, and handle repeated keys correctly.

URL vs URI vs URN: what's the difference?

Mon, 29 Jun 2026 00:00:00 GMT

URI is the umbrella term; a URL locates a resource and a URN names one. Here is how the three relate, with clear examples.

How to URL encode a string

Wed, 01 Jul 2026 00:00:00 GMT

URL encode text so it is safe to put in a link or query string. Learn which characters to encode, the space rule, and when to encode a whole URL vs a value.

What is a query string?

Wed, 01 Jul 2026 00:00:00 GMT

A query string is the part of a URL after the ? that carries key-value parameters. Here is how it is structured, encoded, and used.

What your browser reveals about you

Thu, 02 Jul 2026 00:00:00 GMT

Your browser exposes far more than your IP — screen size, fonts, timezone, and more combine into a fingerprint. Here is what is visible and why it matters.

What is a token in AI language models?

Thu, 25 Jun 2026 00:00:00 GMT

Language models read text as tokens, not words. Here is what a token is, why a word can be several tokens, and why counts vary by model.

What is a context window?

Thu, 25 Jun 2026 00:00:00 GMT

A context window is the maximum amount of text, measured in tokens, that a language model can consider at once. Here is what it includes and why it matters.

How to write a better AI prompt

Mon, 29 Jun 2026 00:00:00 GMT

Clear context, a specific task, and a defined output format make AI prompts far more reliable. Here is a practical structure and the habits that help.

How AI token pricing works

Mon, 29 Jun 2026 00:00:00 GMT

Most AI APIs bill by the token, and input and output are often priced differently. Here is how to reason about cost and estimate it before you run a prompt.

What is prompt injection?

Mon, 29 Jun 2026 00:00:00 GMT

Prompt injection is when hidden instructions in input trick an AI model into ignoring its real task. Here is how it works and how to reduce the risk.

How to compare two texts (diff)

Mon, 29 Jun 2026 00:00:00 GMT

A diff shows what changed between two versions of text: what was added, removed, or kept. Here is how diffs work and when they help.

How to count tokens in a prompt

Wed, 01 Jul 2026 00:00:00 GMT

Estimate how many tokens your text uses before sending it to an AI model. Learn the rough word and character rules and why exact counts vary by model.

What is prompt engineering?

Wed, 01 Jul 2026 00:00:00 GMT

Prompt engineering is the practice of writing inputs that get reliable, useful results from AI models. Here are the core techniques and why they work.

How to write a good YouTube description

Thu, 25 Jun 2026 00:00:00 GMT

A practical structure for YouTube descriptions: a strong first line, useful links, working chapter timestamps, and clean spacing that survives the player.

Social media image sizes that work everywhere

Thu, 25 Jun 2026 00:00:00 GMT

Think in aspect ratios first, then resolution. Here are the dependable shapes for feeds, stories, and thumbnails, and why ratios outlast exact pixel specs.

How to clean up captions and subtitles

Mon, 29 Jun 2026 00:00:00 GMT

Auto-generated captions are full of timestamps, line breaks, and filler. Here is how to turn them into clean, readable text for descriptions and transcripts.

How to write a good video title

Mon, 29 Jun 2026 00:00:00 GMT

A good video title is clear, specific, and fits the space before it gets cut off. Here is how to write one that earns the click honestly.

What is a QR code (and how to make one)?

Wed, 08 Jul 2026 00:00:00 GMT

A QR code is a scannable square barcode that stores a link or text. Here is how QR codes work, what they can hold, and how to create one that scans reliably.

What is the Pomodoro Technique?

Fri, 26 Jun 2026 00:00:00 GMT

The Pomodoro Technique breaks work into focused intervals separated by short breaks. Here is how the cycle works and why the breaks are the point.

What is an .ics calendar file?

Fri, 26 Jun 2026 00:00:00 GMT

An .ics file is a plain-text calendar in the iCalendar format that any major calendar app can read. Here is what is inside one and how events are identified.

How to merge ICS calendar files

Wed, 01 Jul 2026 00:00:00 GMT

Combine several .ics calendar files into one in your browser. Learn when merging helps and how to import the result into Google, Apple, or Outlook.

How to merge PDF files

Mon, 29 Jun 2026 00:00:00 GMT

Combining PDFs into one document is simple when you control the order and keep it local. Here is the workflow and what to watch for.

How to split a PDF

Mon, 29 Jun 2026 00:00:00 GMT

Splitting a PDF lets you pull out pages or break a long document into parts. Here is how to choose ranges and keep it local.

How to rotate PDF pages

Mon, 29 Jun 2026 00:00:00 GMT

Scanned or exported PDFs often come in sideways. Here is how to rotate pages in 90-degree steps and save the fix permanently.

How to convert images to a PDF

Wed, 01 Jul 2026 00:00:00 GMT

Combine JPG or PNG images into a single PDF in your browser. Learn how to order pages, keep quality, and why a PDF is handy for sharing photos.

How to compress a PDF

Wed, 08 Jul 2026 00:00:00 GMT

Shrink a large PDF in your browser so it is easier to email and upload. Learn what makes PDFs large, how compression works, and when quality is affected.

How to extract or delete PDF pages

Wed, 08 Jul 2026 00:00:00 GMT

Keep only the PDF pages you need, or remove the ones you do not, right in your browser. Learn to pick page ranges and save a clean new PDF.

How to blur faces in photos before sharing

Thu, 25 Jun 2026 00:00:00 GMT

A practical guide to hiding faces, license plates, and personal details in a photo, why strong redaction beats a light blur, and how to remove location metadata too.

How to create a strong password

Mon, 29 Jun 2026 00:00:00 GMT

Length beats complexity. Here is how to build passwords that resist guessing, why a manager matters, and the habits that actually keep accounts safe.

How to redact text safely

Mon, 29 Jun 2026 00:00:00 GMT

Redacting text means truly removing sensitive details, not just hiding them. Here is how to do it so the original cannot be recovered.

What metadata is hidden in a PDF?

Mon, 29 Jun 2026 00:00:00 GMT

PDFs carry hidden metadata: author, software, timestamps, and sometimes more. Here is what is in there and how to check and remove it before sharing.

What is metadata, and why remove it?

Mon, 29 Jun 2026 00:00:00 GMT

Metadata is data about your files: who made them, when, and with what. Here is where it hides and why to clear it before sharing.

How to remove metadata from a PDF

Wed, 01 Jul 2026 00:00:00 GMT

Strip hidden metadata — author, software, and timestamps — from a PDF in your browser before sharing it. Learn what a PDF stores and how to clean it.

How to convert audio to MP3

Wed, 01 Jul 2026 00:00:00 GMT

Convert WAV, FLAC, M4A, AAC, OGG, or MP4 audio to MP3 in your browser. Learn how to pick a bitrate and keep quality while shrinking the file.

MP3 vs WAV: which should you use?

Wed, 01 Jul 2026 00:00:00 GMT

WAV is uncompressed and lossless; MP3 is compressed and much smaller. Here is when each makes sense and how to convert between them.

What is audio bitrate?

Wed, 01 Jul 2026 00:00:00 GMT

Audio bitrate is how much data per second an audio file uses, measured in kbps. Here is how it affects quality and file size, and which bitrate to pick.

How to extract audio from a video

Wed, 01 Jul 2026 00:00:00 GMT

Pull the audio track out of an MP4 video and save it as MP3 in your browser. Learn when this works, how to pick a bitrate, and what stays local.