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ARLing NotesEnglish edition62 articles

Guides and articles.

Articles about banking tools, electronic invoices, software integrations, digital books and logic puzzles.

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Articles in this edition
62
Editions
Slovak, Czech, German and English
Newest article
2026-10-20
Published by
ARLing s. r. o., Bratislava

Articles in English. Use the language links to browse the other editions.
Slovenčina Čeština Deutsch English

Articles in English.

Every note lists its sources under the text and ends with a link to the tool or the book it is about. They are grouped by subject, newest first inside each group.

E-invoicing

10 articlesBack to topics
  1. Free Peppol invoice validators compared: what each one checksSeven free Peppol and EN 16931 validators compared: where your file goes, whether the XSD schema is checked, which rules run. Includes the three errors our own checker missed on 25 September 2026.
  2. BR-CO-15 error: fix the invoice total with VATBR-CO-15 means the total with VAT is not the net total plus VAT in the invoice currency. Four causes we reproduced, the exact messages and the fix.
  3. Peppol Invoice Validator: What It Checks and What It MissesWhat a Peppol invoice validator checks, how fatal and warning differ, and what we saw when we broke one sample invoice eleven ways.
  4. CSV invoice batches: check the preview before downloading XMLGroup CSV item rows into invoices, check the batch and inspect previews before downloading UBL XML.
  5. E-Invoicing Mandatory Dates in Germany and SlovakiaTwo separate deadlines now govern electronic invoicing for anyone trading with Slovakia or with Germany,
  6. Peppol Invoice Rejected? Five Fields Worth Checking FirstA Peppol invoice rejected by the receiving side is almost never a random formatting glitch: it fails one specific, documented rule inside EN 16931,
  7. XRechnung vs Peppol BIS Billing 3.0: A Guide for Foreign SuppliersIf your company sits outside Germany and has just won a contract with a German business customer,
  8. How to Create a UBL Invoice Without an ERP SystemIf your accounting software cannot produce a proper electronic invoice yet, you can still create a UBL invoice by hand, field by field,
  9. Peppol Invoice Validation Errors ExplainedWhen a business sends an electronic invoice over the Peppol network, the file has to pass a set of automated business rules before the recipient's system
  10. What Is EN 16931? The Core Invoice Standard ExplainedEN 16931 is the European standard that defines what a compliant electronic invoice must actually contain: the semantic data model of the core invoice,

PDF on an e-ink tablet

9 articlesBack to topics
  1. Puzzles for reMarkable and Kindle Scribe: what to checkPuzzles for reMarkable and Kindle Scribe are PDFs. Where to find them, which kinds suit a pen, what to test in a free sample and what we measured.
  2. PDF form fields: typing, pen notes and what to testHow PDF form fields differ from annotations, which puzzle cells accept typing, and how to test a saved answer using a free Morning Quiet sample.
  3. Testing PDF links on your e-ink tabletTest PDF contents, destinations and return links before and after transfer to an e-ink tablet. What our file checks prove, and what needs your reader.
  4. Reading a novel of 953 pages on an e-ink tablet: what actually mattersWhat actually matters when a novel of 953 pages goes onto an e-ink tablet: line length and type size, a contents you can reach from any page, a band for the pen, and the honest note that the same texts are free as EPUB.
  5. Why an A4 PDF does not fill an e-ink screen, with the arithmeticThe arithmetic behind a page made for an e-ink tablet: 1404 by 1872 dots at 226 dots per inch is 157.8 by 210.4 millimetres, an A4 page shown whole on that screen shrinks to 71 percent, and what else changes when a page is set for glass instead of paper.
  6. Classic novels as PDF for reMarkable and Kindle Scribe: Monte Cristo and Ben-Hur with a notes band on every pageThe Count of Monte Cristo and Ben-Hur typeset for a 157 x 210 mm e-ink page, with a notes band on every page, a linked contents, the text unchanged from a public domain transcription, the measurements of the finished files, and what is not verified yet.
  7. Hyperlinked puzzle PDFs for reMarkable and Kindle Scribe: what changes when the contents page is tappableWhat a tappable contents page changes in a puzzle PDF for an e-ink tablet: a 157 x 210 mm page, 300 puzzles in three levels, Solution links both ways and three layouts of one puzzle set.
  8. Lectio divina journal for reMarkable and Kindle Scribe: the Douay-Rheims text on the page, and room for the penA 31 day Catholic reading book for an e-ink tablet, with the Psalm and the Gospel passage printed on the page from the Douay-Rheims Bible, four steps of lectio divina with lines for the pen, an evening examen, 592 links measured in the file, and what is not verified yet.
  9. Puzzle Planner for reMarkable and Kindle Scribe: one puzzle on every day page of an undated yearAn undated planner and a puzzle book in one hyperlinked PDF for e-ink tablets, 372 puzzles in 10 types, one on every day page of 12 months of 31 days, 941 pages with 4117 internal links, and an honest list of what is not verified yet.

Shop product feeds

6 articlesBack to topics
  1. Description text too short in Google Merchant Center: find the flagged products and every Shopify product with no descriptionMerchant Center lists the flagged products, and the Shopify product export finds every product with no description. Here is how, and what Google asks for.
  2. Missing field "hasMerchantReturnPolicy" and "shippingDetails" on Shopify: what Search Console means and how to fix itWhat the Missing field warnings for returns and shipping mean in Search Console, and three ways to give Google your Shopify return and shipping terms.
  3. Limited performance due to missing identifiers [gtin, mpn, brand] on Shopify: what to fill inGoogle's missing identifiers message on Shopify: where the GTIN, MPN and brand go, and what to do for handmade, custom and vintage products.
  4. An AI shopping assistant for WooCommerce that stores no conversations: what it can answer, what it cannot, and a 10-minute setupAn AI shopping assistant for WooCommerce that answers from your product feed and stores no conversations: what it answers, what it cannot, the 10-minute setup, and pricing.
  5. A Shopify AI shopping assistant built from products.json: how it answers, what it costs, and the theme.liquid setupHow ARLing Asistent reads a Shopify store's public products.json feed to answer shopping questions, the theme.liquid script tag setup, and why there is no separate Shopify App Store app.
  6. Google Merchant Center feed errors explained: the 12 rejections that block most products and how to fix each in the feedThe 12 most common Google Merchant Center and Meta catalog disapprovals, the exact spec rule behind each, and the feed fix for Shopify and WooCommerce.

Other notes

12 articlesBack to topics
  1. AI is now "Super Intelligence" in US federal agencies: what the order requiresOn 29 September 2026 a US executive order told federal agencies to use "Super Intelligence" and "SI" in place of "Artificial Intelligence" and "AI". What the order text requires, what it leaves alone, its one 60-day deadline, and how to change a document without rewriting law titles.
  2. It does not have HTTP ok status: what the CORS preflight (OPTIONS) request needsWhy Chrome says the preflight does not have HTTP ok status, which server layer turns your OPTIONS request into a 401, 404, 405 or 500, and how to answer it with a 2xx.
  3. Redirect is not allowed for a preflight request: CORS, redirects and the trailing slashWhy Chrome refuses a CORS preflight that gets a 3xx, how to find the redirect with one curl command, and the usual causes: a trailing slash, www, https or a login page.
  4. Request header field is not allowed by Access-Control-Allow-Headers: fixing the preflight allow-listWhy the CORS preflight rejects a request header such as Authorization or Content-Type, how to read the full list the browser asked for, and how to fix Access-Control-Allow-Headers.
  5. Access-Control-Allow-Origin '*' with credentials mode 'include': why cookies need an exact originWhy browsers reject Access-Control-Allow-Origin: * on requests with cookies, where the * comes from in Express or Laravel, and the two headers that fix it.
  6. ERR_TOO_MANY_REDIRECTS: find the two rules redirecting to each other (Cloudflare, nginx, proxies, WordPress)ERR_TOO_MANY_REDIRECTS means two layers keep undoing each other's redirect. Read the loop with curl, then fix the Cloudflare, nginx, proxy or WordPress rule behind it.
  7. "The given origin is not allowed for the given client ID": Sign In With Google and JavaScript originsGoogle Identity Services logs this when the scheme, host and port of your page match no entry in Authorized JavaScript origins. The causes in order, and the fix for each.
  8. JWT "invalid signature": wrong secret, wrong key, or the wrong algorithmWhat JsonWebTokenError: invalid signature rules out, the four byte mismatches behind it, and how to prove which one you have before you change any code.
  9. "jwt malformed": what your verifier received instead of a tokenjsonwebtoken throws jwt malformed when the value does not split into three parts at the periods. What arrived instead of a token, and the fix for each case.
  10. Set-Cookie blocked because of SameSite=Lax: fixing a session cookie from a cross-site APIWhy Chrome drops a Set-Cookie without SameSite from a cross-site API response, how to tell cross-site from cross-origin, and the two routes that fix it.
  11. No 'Access-Control-Allow-Origin' header is present: which response is missing it, and the fixWhy the browser says No 'Access-Control-Allow-Origin' header is present, and how to find whether the preflight, a redirect or an error response lacks it.
  12. Public domain in practice: what it means for Ben-Hur and Monte CristoTwo questions hide inside public domain: whether the work is free and whether the copy in your hands is. The dates for Ben-Hur and The Count of Monte Cristo, the seventy year rule in the European Union, and the licence clause that makes a transcription a separate matter.

Where these notes come from

We write them beside the work on our own tools and books. These are those things.

  1. The ARLing shopPuzzle books, classic novels and journals. Every title has a free sample.Browse
  2. Puzzle Post100 hyperlinked puzzles a month for an e-ink tablet.3.90 € a month