Writing

Notes on engineering, product thinking, and lessons learned,
shared across note, Zenn, Qiita, and a personal blog.

Featured

Featured

Is a 1024-bit DKIM Key Enough? RFC Requirements and What Domains Actually Publish

Blog JP Jul 27, 2026
Read article
SourceTitleLangPublishedLink
Blog Blackout Curtains for Sleep: Fit, Light Leaks & What to Check Before You Buy JPEN Oct 16, 2026
Blog Standardizing www and Non-www: DNS, Certificates, and Redirects in Order JP Oct 15, 2026
Blog How to Convert PDF to Markdown: A Guide for Scans, Columns, Tables, and Images JPEN Oct 13, 2026
Blog Alarm Clock Without a Smartphone: How to Choose One JPEN Oct 8, 2026
Blog Fixing a Site Not Served Over HTTPS — Certificate, Redirect, and Display, in Order JP Oct 4, 2026
Blog Fixing SSL Certificate Name Mismatches and Trust Errors — Old TLS Included JP Sep 28, 2026
Blog How to Block AI Crawlers in robots.txt — GPTBot vs. AI Search Crawlers and What Happens When You Do JP Sep 24, 2026
Blog Site Not Indexed Because of robots.txt: How to Find Disallow: / and Verify the Fix JP Sep 13, 2026
Blog Expired SSL Certificate — How to Renew and Troubleshoot Warnings That Won't Clear JP Sep 10, 2026
Blog Do Wake-Up Lights Work? What Research Shows and How to Choose JPEN Sep 7, 2026
Blog When an MX Target Won't Resolve: Causes, Fixes, and Raw IP Addresses JP Sep 5, 2026
Blog Nameserver Mismatch or Mixed Providers — 4 Steps to Verify DNS Delegation JP Sep 2, 2026
Blog MX Record Priority: Lower Numbers Come First — Handling Equal Values and Single Records JP Aug 27, 2026
Blog Can't Sleep Hungry? What to Eat Before Bed, and How Much JPEN Aug 24, 2026
Blog SPF Void Lookup Limit: When a Third Lookup Triggers PermError JP Aug 23, 2026
Blog Fixing SPF Record Syntax Errors — How to Identify the Problem and Replace ptr JP Aug 22, 2026
Blog SPF Record all Qualifier Explained: ~all vs -all — Which Should You Use JP Aug 19, 2026
Blog "DKIM May Not Be Configured" — 3 Steps to Verify It JP Aug 17, 2026
Blog SPF Passes but DMARC Fails — How to Check Alignment JP Aug 17, 2026
Blog When "DMARC Is Not Functional" Appears — What You're Missing Is SPF and DKIM JP Aug 17, 2026
Blog DMARC pct Tag Deprecated — What RFC 9989 Changed and How to Fix It JP Aug 17, 2026
Blog CBT-I App Cost: Free, Subscription, and Prescription Options JPEN Aug 16, 2026
Blog Online Sleep Doctor Cost: Published Prices and What Medicare Pays JPEN Aug 16, 2026
Blog DKIM Authentication Failures — When the Record Exists but Validation Still Fails JP Aug 16, 2026
Blog DMARC Record Format Errors — Spotting Duplicate Records, p Tag Issues, and Invalid Values JP Aug 16, 2026
Blog Gmail POP Receiving Sunset: When It Ends, Who It Affects, and How to Verify It's Not Happening to You JP Aug 16, 2026
Blog CPAP Machine Cost: List Prices, Replacement Parts, and Medicare JPEN Aug 15, 2026
Blog At-Home Sleep Apnea Test Cost: Published Prices and Medicare's Share JPEN Aug 15, 2026
Blog How Much Does a Sleep Study Cost? Cash, Insurance & Medicare JPEN Aug 15, 2026
Blog Gmail POP Fetch Retirement: Choosing Between Forwarding, IMAP, and Google Workspace JP Aug 15, 2026
Blog At-Home Sleep Study Costs — Insurance Coverage and How to Borrow the Device JPEN Aug 10, 2026
Blog Online Insomnia Consultation Fees — Insurance Coverage and Medications You Can't Get at a First Visit JPEN Aug 10, 2026
Blog How Much Does a First Visit to a Sleep Clinic Cost — Consultation, Tests, and Out-of-pocket Fees JPEN Aug 10, 2026
Blog Do Subdomains Need DMARC? How the sp Tag Works and What It Inherits JP Aug 10, 2026
Blog CPAP Monthly Costs: What You Pay with Japanese Insurance and the 30% Co-pay Breakdown JPEN Aug 9, 2026
Blog Sleep Apnea Mouthguard Costs: Insurance Coverage Conditions and What to Expect at 30% Copay JPEN Aug 9, 2026
Blog Sleep Apnea Testing Costs — Screening vs. Diagnostic Exam Fees and Patient Copays JPEN Aug 9, 2026
Blog Publishing a Static Site for Free on Cloudflare Pages JP Aug 7, 2026
Blog ColorfulBox Pricing: Why BOX2 Looks Cheaper Than BOX1 JP Aug 7, 2026
Blog ConoHa WING Pricing: The WING Pack Can't Be Cancelled Midway JP Aug 7, 2026
Blog Lolipop Pricing: What ¥55 a Month Buys You JP Aug 7, 2026
Blog mixhost Pricing: The ¥495 a Month Rate Is First-Term Only JP Aug 7, 2026
Blog Netlify Pricing: How the Credit System Works JP Aug 7, 2026
Blog Sakura's Rental Server Pricing: Which Plan Runs WordPress JP Aug 7, 2026
Blog Star Server Pricing: What's Missing From the ¥253 Light Plan JP Aug 7, 2026
Blog Vercel Pricing: The Free Hobby Plan Is for One Person JP Aug 7, 2026
Blog Xserver Pricing: The Monthly Rate Doubles With Contract Length JP Aug 7, 2026
Blog BASE Pricing: What Costs Money at ¥0 a Month, and Where It Gets Expensive JP Aug 6, 2026
Blog Jimdo Pricing: AI Builder vs. Creator JP Aug 6, 2026
Blog Peraichi Pricing: Which Plan Includes a Blog JP Aug 6, 2026
Blog Shopify Pricing: Two Fees on Top of the Monthly Rate JP Aug 6, 2026
Blog Wix Pricing: The Cheapest Plan Has No Store or Booking JP Aug 6, 2026
Blog Choosing a Web Agency: Read the Quote's Scope, Not Just the Price JP Aug 6, 2026
Blog How Far Can a Free Website Go? Where ¥0 Plans Stop JP Aug 6, 2026
Blog Why Website Updates Stop: Choosing by Frequency and Who Updates JP Aug 6, 2026
Blog Getting a Custom Domain: Cost, and .com vs. .jp JP Aug 6, 2026
Blog Starting an Online Shop: BASE and Shopify Charge Differently JP Aug 6, 2026
Blog Can You Move Your Website to Another Service? Portability by Approach JP Aug 6, 2026
Blog WordPress vs. STUDIO: Comparing Across 5 Axes JP Aug 6, 2026
Blog Is SPF Enough? 3 Cases Where DKIM Is Needed — and What to Do If You Cannot Add It JP Aug 6, 2026
Blog DNS Cutover for Mail Server Migration — The Right Order to Change MX, SPF, and DKIM Records (and How to Roll Back) JP Aug 3, 2026
Blog What Is STUDIO? Where the Free Plan Ends JP Aug 2, 2026
Blog How to Choose a Website Approach: 5 Conditions That Decide It JP Aug 2, 2026
Blog How Much Does a Website Cost? Setup and Monthly Fees by Approach JP Aug 2, 2026
Blog Why PDF Tables Break When You Convert to Markdown (7 PDFs Tested) JPEN Aug 2, 2026
Blog Setting Up DMARC Report Receiving — How to Write the rua Tag and When You Can Skip It JP Aug 2, 2026
Blog DMARC Risks When You Skip It — A Starter Configuration to Begin With JP Jul 30, 2026
Blog Yoga Nidra for Sleep: A 15-Minute Script You Can Read Yourself JPEN Jul 29, 2026
Blog Is a 1024-bit DKIM Key Enough? RFC Requirements and What Domains Actually Publish JP Jul 27, 2026
Blog How to Find Your DKIM Selector — Reading d= and s= from Mail Headers JP Jul 27, 2026
Blog What DKIM's t=y (Testing Mode) Means — What to Check Before Removing It JP Jul 27, 2026
Blog Why DMARC Reports Never Arrive — External Addresses Need the Receiver's Authorisation JP Jul 27, 2026
Blog DNS Changes Not Showing Up? Compare Two Answers Before Touching the Settings JP Jul 27, 2026
Blog Fixing Gmail's 550-5.7.26 Rejection — Three Causes Behind One Code JP Jul 27, 2026
Blog Why Your Domain's Mail Lands in Spam — Separating Authentication from Everything Else JP Jul 27, 2026
Blog Why an MX Record Must Not Point to a CNAME — A Rule Separate from Zone Apex JP Jul 27, 2026
Blog What Is Null MX? Settings for Domains That Receive No Mail, and Spoofing Defence JP Jul 27, 2026
Blog SPF PermError — Why DNS Lookups Exceed 10 and How to Count Them JP Jul 27, 2026
Blog Mail from Your Own Domain Isn't Delivered? Check Sending and Receiving Separately JP Jul 26, 2026
Blog JSON to CSV — Nested Objects, Arrays and Nulls Measured on 4 Converters JPEN Jul 26, 2026
Blog How to Become a Morning Person: Timeline and 4-Week Plan JPEN Jul 20, 2026
Blog Migrate Articles Between Dev.to, Hashnode, and Medium — What Each Export Gives You JPEN Jul 20, 2026
Blog Night Shift Sleep Schedule Examples: Fixed, 12-Hour and Rotating JPEN Jul 19, 2026
Blog Gmail & Outlook Email to Markdown — No Upload JPEN Jul 17, 2026
Blog Body Scan Meditation for Sleep: 10- and 3-Minute Scripts JPEN Jul 15, 2026
Blog Pink Noise vs White Noise: What a 2026 Sleep Study Changed JPEN Jul 15, 2026
Blog Stretches Before Bed: Timed 10-Minute Routine (No Standing) JPEN Jul 15, 2026
Blog Markdown Escape Characters: Pipes, Tables & 23 Tested Cases JPEN Jul 15, 2026
Blog Export WordPress Posts to Markdown With or Without Node.js JPEN Jul 12, 2026
Blog Notion Export to Markdown — Fix UUIDs & Callouts, No Upload JPEN Jul 6, 2026
Zenn Building Trust in Health-adjacent Apps: On-device Anonymization, Static SSG, and Anonymous Sharing JP Jul 4, 2026
Qiita Anonymizing Just the Mouth Region with Vision Framework — Building an Orthodontic Record App JP Jul 4, 2026
note How I Built an Orthodontic Tracker That Keeps Your Face Private JP Jul 4, 2026
Blog How Long Should You Snooze? 15 Minutes or 90 Minutes JPEN Jun 29, 2026
Blog How to Recover From an All-Nighter: 20-Minute Nap or 90? JPEN Jun 27, 2026
Blog Markdown Frontmatter YAML to JSON — 5 SSGs, 5 YAML Traps, No Upload JPEN Jun 22, 2026
Blog API JSON to Markdown Table — curl, jq, Pagination, 6 Response Shapes JPEN Jun 21, 2026
Blog YAML vs Markdown vs JSON vs CSV: Data Format Comparison JPEN Jun 18, 2026
Blog Paste HTML as Markdown — Clean Copy from Web, Remove Spans / Inline Styles / Word Cruft (Browser) JPEN Jun 16, 2026
Blog Markdown Table Not Rendering or Broken? Fix It by Symptom JPEN Jun 14, 2026
Blog Cognitive Shuffle for Sleep: How to Do It (Full Example) JPEN Jun 13, 2026
Blog 10-3-2-1-0 Sleep Rule: Does It Work, and How to Adjust It JPEN Jun 12, 2026
Blog Military Sleep Method: A One-Pass Script and the 2-Minute, 96% Claims JPEN Jun 12, 2026
Blog How to Do 4-7-8 Breathing Before Bed: 4 Rounds and Adjustments JPEN Jun 11, 2026
Blog Warm Bath or Shower Before Bed: 90-Min Timing and Chart JPEN Jun 11, 2026
Blog Bedtime Journaling: A 5-Minute Printable Template + Example JPEN Jun 10, 2026
Blog How Long Should a Power Nap Be? 10, 20 or 30 Minutes JPEN Jun 10, 2026
Blog JSON Trailing Comma: Find the Line, or Switch to JSONC JPEN Jun 8, 2026
Blog HTML Table to Markdown Converter — Pipes, Line Breaks & Uneven Rows JPEN Jun 6, 2026
Blog Excel to Markdown Table Converter — Paste Cells, No Upload JPEN Jun 5, 2026
Blog Miracle Morning SAVERS: 6 to 60 Minute Routines (No 5 AM) JPEN Jun 4, 2026
Blog Caffeine Tolerance Reset: How Long It Takes and a 7-Day Taper JPEN Jun 2, 2026
Blog How to Convert JSON to a Markdown Table — Arrays, API Responses, Nested Data JPEN Jun 2, 2026
Blog Online JSON Converter Security: 5 Checks Before Pasting Secrets (2025 Breach Data) JPEN Jun 2, 2026
Blog Weekend Sleep-In, Rough Monday? How to Ease Social Jet Lag JPEN May 30, 2026
Blog Ideal Bedroom Temperature for Sleep: 60–67°F (16–19°C) JPEN May 29, 2026
Blog How to Wake Up Refreshed: 5 Habits to Start Tonight JPEN May 29, 2026
Blog Minimum Sleep Required: 7+ Hours for Most Adults JPEN May 25, 2026
Blog Markdown vs HTML for LLMs: ~70% Fewer Tokens, and Your HTML Stays Local JPEN May 21, 2026
Qiita What I Learned Running 1B–4B LLMs on iPhone — 7-Model Benchmarks and Why I Gave Up JP May 17, 2026
Blog How Long Does It Take to Fall Asleep? The 10-20 Minute Range JPEN May 17, 2026
Blog CommonMark vs GitHub Flavored Markdown (GFM): Differences and Examples JPEN May 13, 2026
Blog GFM Tables: Pipe Syntax, Empty Cells & Line Breaks That Render JPEN May 13, 2026
Blog How Long Does Caffeine Last? Bedtime Cutoff by Dose JPEN May 7, 2026
Qiita StoreKit 2 + Server-side JWS Verification: Designing a Zero-trust Freemium Billing System JP May 5, 2026
Zenn Freemium AI App Monetization: Two-Tier Pricing with 80B Free and Sonnet Paid — Breaking Down the Break-Even Math JP May 4, 2026
Zenn Next.js 16 Turbopack + Claude in Chrome: How VS Code Looked Like 180GB JP May 3, 2026
note Sharing Love Chats with AI Feels Risky — The Privacy Design Behind It JP May 3, 2026
Qiita Cognito Anonymous Auth + Server-side Signup — Building a No-login iOS App Safely JP May 2, 2026
Blog GitHub README Table: Make One from CSV or JSON JPEN Apr 27, 2026
Blog HTML to Markdown Guide: Tags, Tables, Tools & Limits JPEN Apr 27, 2026
Blog GitHub Markdown Table Syntax: Copy-Paste Examples & Fixes JPEN Apr 27, 2026
note Asking AI for Relationship Advice — How It Differs from Human Advice JP Apr 25, 2026
Blog Beginner Evening Routine Guide: 3 Templates, 7 Mistakes JPEN Apr 25, 2026
Blog How to Stop Using Your Phone Before Bed (Without Quitting) JPEN Apr 25, 2026
Blog How Long Is a Sleep Cycle? 90 Minutes, 80–110 Range, Stages JPEN Apr 25, 2026
Qiita Multi-model Routing with Amazon Bedrock Converse API — A Two-tier Design with Qwen3 80B (Free) and Claude Sonnet 4.6 JP Apr 24, 2026
Qiita Local OCR + Cloud LLM: A Hybrid Architecture for an iOS App That Never Uploads Images JP Apr 22, 2026
Zenn Building Evidence-based Psychology into an LLM Prompt — Designing a Relationship Analysis AI JP Apr 21, 2026
Blog What Time Should I Go to Bed to Wake Up at 6 AM? Bedtime Chart JPEN Apr 21, 2026
Blog Can't Fall Asleep? The 20-Minute Rule and 5 Things to Try Tonight JPEN Apr 21, 2026
Blog How Long Does Sleep Debt Take to Recover? A 1–2 Week Plan JPEN Apr 21, 2026
note Hitting the Limits of Local LLMs and Ending Up with Cloud AI JP Apr 20, 2026
Qiita Don't Let LLM JSON Output Break You — A Multi-stage Decoder & Auto-repair Parser (Swift Codable) JP Apr 19, 2026
Blog How Long Does Jet Lag Last? Recovery Days, East vs West JPEN Apr 19, 2026
Blog Why Do You Wake Up Tired After 8 Hours of Sleep? 7 Reasons JPEN Apr 19, 2026
Blog 30-Minute Wind-Down Routine, Set to Tonight's Bedtime JPEN Apr 19, 2026
Qiita A Complete Guide to Implementing Three-tier (Free / Basic / Pro) Subscriptions with StoreKit 2 JP Apr 18, 2026
note How a New TikTok Account Stayed at 0 Views for a Week — 4 Pitfalls and the Moment They Cleared JP Apr 17, 2026
Blog How to Convert CSV to a Markdown Table JPEN Apr 17, 2026
Blog Markdown to HTML in JavaScript — marked.js, markdown-it, Pandoc (with GFM) JPEN Apr 17, 2026
Zenn Architecture of a Screenshot-to-AI Analysis App — iOS MVVM + AWS Serverless for a Relationship Analysis AI JP Apr 15, 2026
Qiita Detecting the Sender from Apple Vision OCR boundingBox — Structuring a Chat Screenshot JP Apr 15, 2026
note Building a Relationship-analysis AI App to Calm the Fear of Being Left on Read JP Apr 15, 2026
Blog Does JSON Allow Comments? 4 Alternatives That Work JPEN Apr 13, 2026
Blog 'Forbidden Block Composed Value' in YAML: The Fix JPEN Apr 13, 2026
Qiita SFSpeechRecognizer timestamp=0 Bug and How to Work Around It — Why You Should Only Trust isFinal Results JP Apr 10, 2026
note Building and Shipping an Indie iOS App to the App Store — A Full Solo Log JP Apr 10, 2026
Blog Curl Pretty Print JSON: jq, json.tool, formatarc CLI & Browser JPEN Apr 10, 2026
Qiita Building a Fully On-device English Subtitle Generator with Speech and Translation Frameworks JP Apr 7, 2026
note An Engineer Bad at English Built an English Learning App for Himself JP Apr 7, 2026
Blog Best JSON Viewer & Formatter Chrome Extensions (2026): 7 Tested JPEN Mar 25, 2026
Qiita Converting CSV API Responses to JSON and Processing Them with jq JP Mar 24, 2026
Qiita How to Debug When You Get Stuck on Kubernetes YAML JP Mar 22, 2026
Medium How I Debug Malformed JSON from APIs EN Mar 21, 2026
Qiita 3 Ways to Pretty-print curl JSON Responses Instantly JP Mar 20, 2026
Zenn Building an Indie Data-conversion Site — From SEO Design to Publishing on npm JP Mar 20, 2026
Medium Building a Static Data Converter Site with Next.js EN Mar 20, 2026
Blog Chrome Extension to Convert JSON, YAML & CSV JPEN Mar 20, 2026
Blog formatarc — Format JSON, YAML & CSV from the Terminal (npm / npx) JPEN Mar 20, 2026
Blog JSON Pretty Print — Free Online JSON Formatter, jq & Code Examples (2026) JPEN Mar 20, 2026
Blog How to Write JSON: A Complete Syntax Guide JPEN Mar 20, 2026
Blog CSV File Format: Example, Quoting Rules and Encoding JPEN Mar 20, 2026
Blog What is JSON? Syntax, Data Types, and Real-World Uses (2026 Guide) JPEN Mar 20, 2026
Blog What Is YAML? Syntax, Comments & Practical Examples JPEN Mar 20, 2026
Blog YAML vs JSON: Four Parsers, Four Different Answers (2026) JPEN Mar 19, 2026
Blog JSON Parse Error: Fix Unexpected Token, End of Input & HTML Responses JPEN Mar 18, 2026
Blog Python YAML to JSON: safe_load, Multi-Document YAML & Type Pitfalls JPEN Mar 17, 2026
Blog Convert CSV to JSON — Browser, Python, Node, Go, Miller (No Upload) JPEN Mar 16, 2026
Blog Convert JSON to YAML — Kubernetes, Docker Compose, Ansible (Browser & CLI) JPEN Mar 15, 2026
180 entries total