Articles

Office expense reports, school assignments, signed contracts — merging photos into a single PDF is a daily need. "Image to PDF" sounds simple but has plenty of gotchas: will HEIC open, A4 vs Letter, N-up layout to save paper, will the printer crop margins. This guide uses our `image-to-pdf` tool as the worked example, covers each detail in one place, and runs entirely **client-side — your files never leave the browser**.

Embedding images directly into HTML / CSS / JSON — Base64 has been the front-end engineer's image-bundling tool for 15 years. But when does inlining actually help, and when does it hurt? What exactly is a Data URI? Why must email images be inline? This guide uses our `image-base64` tool as the worked example to clarify Base64's real use cases and avoid three classic misuses.

"Does my prompt fit?" "How much will it cost?" "Will I blow the context window?" — three questions every AI app developer has been asked by their PM. But OpenAI / Anthropic / Google all tokenize differently, and Chinese vs English tokens differ even more. This guide uses our `token-counter` tool as the worked example to break down real token-estimation logic, the cost comparison across 5 leading models, and 3 practical cost-saving techniques.

The worst part of drawing flowcharts isn't drawing — it's changing them. Lucidchart drag-and-drop, Excalidraw rebuilds — every requirement change starts over. **Mermaid describes diagrams in plain text**: version control, git diff, multi-person collaboration — all solved. This guide uses our `mermaid-editor` tool as the worked example, covering syntax for the 7 diagram types, 3 gotchas I've hit, and how it integrates with GitHub / Notion / Confluence.

"I sent you photos but you can't open them?" — this conversation happens a million times a day between iPhone and Android / Windows users. **HEIC is Apple's default photo format since iOS 11** — better compression than JPG but worse compatibility. This guide covers HEIC's design rationale, when to convert to JPG, three batch conversion methods, and the details around preserving EXIF metadata.

JWTs are the most widely adopted stateless authentication standard of the past decade — and one of the most frequently misused protocols on the OWASP Top 10. From a QA angle, understanding the structure is what turns vague "test auth" tickets into concrete security test cases.

regex is something most engineers use daily but never feel fully fluent in. Here are the techniques I actually reach for after years of QA / SRE work — plus the real cases where my browser locked up because of one careless quantifier.

The painful part of E2E automation isn't writing steps — it's selectors that break every other day. Here are the patterns that worked across years of writing, debugging, and migrating Selenium / Cypress / Playwright suites, plus why Playwright pushes role-based locators.

When a QA or SRE team gets the first batch of load-test numbers, the question is always the same — "is this normal?" Here's how percentiles became the core of SLOs in industry, and how to read them.

Doing QA in fintech, e-commerce, or government projects means generating volumes of test data — but using real personal data is a violation of PDPA / GDPR. This article covers why fake data is required, the Taiwan official checksum algorithms, and real QA scenarios where this data matters.