ToolHQ Blog
Hướng dẫn, bài học và mẹo để tận dụng tối đa các công cụ trực tuyến miễn phí. 194 bài viết.
194 articles — page 3 of 9
She Published the Same Article Twice. The Second Title Drove Four Times the Traffic.
Upworthy's 8,977-headline archive reveals what makes titles work. The answer is an information gap, and it has a precise optimal point research has now mapped.
When the Document Is a Thousand Pages but the Evidence Is on Pages 74 Through 78
Why extracting specific pages from a PDF matters in litigation, academic research, and compliance audits, and what makes the process technically non-trivial.
Six Major Platforms. Six Different Aspect Ratios. Here Is How to Crop One Video for All of Them.
YouTube wants 16:9. Instagram wants 9:16. TikTok wants 9:16. LinkedIn wants 1:1. Here is what cropping actually does to your video and how to handle multi-platform distribution.
30 Business Days Is 40 Percent Longer Than 30 Calendar Days. Most Contracts Do Not Specify.
When a contract says '30 days' without specifying which kind, the default is calendar days. Here is how the two diverge and why it matters for deadlines.
XML Is Verbose by Design. JSON Is Concise by Design. Here Is What You Lose When You Convert.
XML and JSON represent the same data differently. A typical XML document is 2-4x larger than the equivalent JSON. Here is what features cannot survive the conversion.
camelCase, snake_case, and kebab-case: Why Programmers Cannot Agree on a Simple Naming Rule
Why programmers use camelCase, snake_case, and kebab-case — and why they can't agree. The history of naming conventions from Bell Labs to modern JavaScript.
Whitespace in HTML Is Semantic, Not Decorative. Formatting It Correctly Requires Knowing the Difference.
Whitespace between inline HTML elements changes what appears on screen. A formatter that normalizes it aggressively can break your layout. Here is how to format HTML safely.
Four Formulas Give Four Different Answers for Ideal Weight. None of Them Were Designed for Fitness.
Hamwi, Devine, Robinson, and Miller were all created for drug dosing or insurance actuarial tables, not fitness targets. Here is what each formula actually measures.
Your IP Address Shows Where Your Connection Is Registered, Not Where You Are. Here Is the Difference.
IP geolocation maps IP address registrations, not GPS positions. Country detection exceeds 99%. City-level accuracy varies by carrier and region. Here is why.
Your JWT Payload Is Not Encrypted. A 2015 Bug Let Attackers Change It by Setting the Algorithm to 'None'.
JWT payloads are Base64-encoded, not encrypted. Anyone with the token can read your user ID and role. A 2015 vulnerability let attackers bypass signature verification entirely.
400 Product Listings, 6-Second Load Times, and What Changing an Image Format Fixed
How converting PNG product images to WebP affects Core Web Vitals, Google rankings, and conversion rates. A practical breakdown for e-commerce sites.
Was the Investment Worth It? The ROI Formula Is Simple. The Answer Depends on What You Count.
ROI is net profit divided by cost. But what counts as profit and what counts as cost are decisions, not math. Here's why consistent definitions matter more than the formula.
The United States and Canada Are the Last Major Countries Still Using Letter-Size Paper. Here Is What Happens to Documents Crossing the Divide.
The US uses Letter, the world uses A4. That small size difference breaks documents constantly. Here is what resizing a PDF actually does and when you need it.
A Startup Chose Blue Because It Looked Professional. Here Is the Problem With That Logic.
The same reasoning that makes blue feel safe makes it the default for every competitor in your market. Here is what color research actually says about brand differentiation.
The Float-Clearing Hack Ran Production CSS for 15 Years. Flexbox Solved It in One Property.
Web developers used float hacks for column layouts for 15 years. Flexbox was specifically designed to solve those problems. Here is how it works and where it still trips developers.
Google Bought a Video Company in 2009. The Result Is Now the Web's Default Image Format.
WebP came from Google's 2009 acquisition of On2 Technologies and its VP8 video codec. Here's how video compression technology became the web's standard image format.
The Page Looked Fine. The Google Preview Was a Random Sentence from Paragraph 7.
Meta keywords were killed by Google in 2009. Meta descriptions, viewport tags, and Open Graph tags still matter. Here is the complete picture of what each tag does.
PDF Stores Instructions. PNG Stores Pixels. Here Is Why Resolution Is the Only Setting That Matters When Converting.
A PDF page does not exist as an image until a viewer renders it. When converting to PNG, the resolution you choose determines everything. Here is how to choose the right DPI.
Why Your WebP Files Open in Browsers but Nothing Else
WebP is everywhere on the web but incompatible with most photo software. Here's why the format gap exists and what to do when your images won't open.
Why Does a Web Page Look Perfect in Chrome But Break When You Print It to PDF? Here Is What the Browser Does Differently.
Browser print-to-PDF suppresses backgrounds, ignores page breaks, and reflows layouts. Here is what a dedicated HTML-to-PDF converter does that browsers cannot.
A Chinese Cryptographer Broke MD5, MD4, and Two Other Hash Functions in One Day in 2004. Here Is What Happened Next.
In August 2004, Xiaoyun Wang announced collision attacks on MD5 at CRYPTO 2004. Here is what hash collisions mean, which uses are still safe, and when SHA-256 is required.
JPG or PNG for Your iPhone Photos? The Answer Depends on What You Are Doing With Them.
PNG and JPG solve image storage differently. The right choice depends on your use case, especially if you need transparency or plan to edit the image repeatedly.
What Does a Broken Link Actually Cost? The Answer Has Three Parts.
Broken links waste crawl budget, interrupt authority flow, and degrade user experience. A JAMA study found 50% of cited links go dead within 5 years. Here is what to do.
A Well-Commented CSS File Is 30 to 50 Percent Larger Than It Needs to Be. Here Is What Gets Removed.
CSS comments, whitespace, and verbose values exist for humans and are ignored by browsers. Minifying removes them and can cut file size by up to 50 percent before gzip.