Marathonbet Promo Code WELCOME100 carries a 500% deposit bonus and 300 free spins on the casino side of the account, and it can be entered from a phone just as it can from a desktop — provided you know where the field hides on a small screen. This guide is written for readers who register, deposit and play almost entirely from a handset, because that is where most sign-ups now happen and where most code-entry mistakes are made. The code itself does not change between devices. What changes is the layout, the number of taps between you and the promo field, and the handful of small behaviours that only show up on mobile.
What the code is attached to
WELCOME100 is tied to the casino welcome package: a staged 500% match spread across five deposits, plus 300 free spins. It is not the sportsbook offer. Marathonbet runs a separate sports promotion, historically structured as a free bet released by turning over a qualifying deposit on accumulators with a minimum number of legs, each above a minimum odds threshold. You normally choose one or the other at registration, and you generally cannot swap afterwards.
That matters more on mobile than it sounds. On a phone, the offer selection is often presented as a short list of tappable cards or radio buttons, sometimes below the fold, and it is easy to scroll past a pre-selected default without registering that you have just made a permanent choice. Before you tap through the final confirmation, scroll back up and check which offer is highlighted.
App or mobile browser: which to register in
Both routes lead to the same account, and the code is the same string in either. The practical differences are usually these:
A mobile browser gives you the full registration form as the operator built it for the web, which means the promo code field is present in the same place in the flow as on desktop, just stacked vertically.
In an app, registration is sometimes condensed into several short steps, and optional fields such as a promo code can sit behind a collapsed row or an extra screen.
Browsers let you paste from the clipboard reliably and let you open the terms in a second tab without losing your place in the form.
Apps tend to handle push notifications and live features more smoothly once the account exists, which is a reason to install after registering rather than before.
A reasonable approach is to register in a mobile browser, where you can see every field at once and check the offer selection, then install the app afterwards for day-to-day use. Nothing about WELCOME100 requires one device or the other.
Where the promo field lives on a small screen
Desktop registration forms usually place a promo code box in the same visual block as the offer choice. On a phone, that same block becomes a vertical stack, and the code box commonly ends up in one of three places: at the bottom of the personal-details step, on a separate screen immediately after the offer selection, or behind an expandable row labelled along the lines of "have a promo code". Collapsed rows are the usual culprit when people say they could not find anywhere to type the code — the row is there, it simply looks like a heading until you tap it.
Type or paste WELCOME100 exactly as written, in capitals, with no spaces. Mobile keyboards are the main source of error here. Autocapitalise can leave the form field with a leading capital in an unintended place, autocorrect occasionally tries to break the string into two words, and predictive text can insert a trailing space you cannot see. If the field accepts the entry but nothing appears to change, close the keyboard and read the characters back before moving on.
Mobile-only quirks worth knowing
Small screens introduce problems that never arise on a laptop. These are the ones to plan around:
Autofill overwriting fields. Password managers sometimes populate adjacent boxes when they misread a form, which can clear or corrupt a code you already typed. Enter the promo code last, after the rest of the form is filled.
Session loss on app switching. Leaving the browser to check a message and returning can reload the form. If that happens, re-check that the code and the offer selection survived.
Currency selection buried in a dropdown. Currency usually cannot be changed later, and on mobile it is often a native picker that scrolls fast under a thumb. Confirm it reads what you intended before submitting.
Terms opened in an in-app viewer. Tapping a terms link inside an app can open an overlay that, when closed, drops you back at the start of the flow. Read the terms before you begin, or open them in a browser tab alongside.
Verification documents. Identity verification is easier on a phone than anywhere else, since the camera is already there. Doing it at registration rather than when a withdrawal is pending removes the most common cause of payout delay.
Step by step from a handset
Open the official Marathonbet site for your country in your mobile browser and start registration.
Fill in your personal details, then set your currency deliberately — it usually cannot be changed later.
Choose the casino welcome offer if the 500% package and 300 free spins are what you want, or the sports offer if you are here to bet. The two are mutually exclusive.
Find the promo code field, expanding any collapsed row if necessary, and enter WELCOME100 in capitals with no spaces.
Submit the form, then complete identity verification straight away using the phone camera.
Deposit at least the stated minimum and confirm on screen that the offer and its terms have attached before you play.
Install the app afterwards if you prefer it for everyday use.
Sizing the deposit on a phone
The casino package is staged across five deposits, and the full 500% headline is unreachable without €5,000 in deposits. The rollover is reported at 35x on bonus credit, with a separate 30x on free-spin winnings. A 35x requirement means that for every unit of bonus credit you hold, thirty-five units must be turned over before it becomes withdrawable — so the sum to run is not the headline percentage but your own deposit multiplied out against that figure.
This is worth doing before you tap deposit rather than after. Phones encourage fast decisions, and stored card details or a wallet button can turn a deposit into a two-tap action. Work out the number on the calculator app first, size the deposit to a rollover you can realistically clear, and remember that declining both welcome offers keeps your balance withdrawable and unencumbered — frequently the sensible answer if you are unsure.
Mobile betting features and banking
If you take the sports route instead, the mobile experience is where Marathonbet's sportsbook strengths show. The book covers well over twenty sports with pre-match and in-play markets, and includes cash out, bet editing and live streaming of a wide range of events — all features that are used far more often from a phone than a desk. Coverage runs deepest on football and tennis, which is also where the pricing is tightest: margins are publicised at around 1.5% on football and tennis and roughly 2.3% across the book, against typical bookmakers operating several points higher. A tighter margin improves every price you take rather than one deposit, which is why regular bettors often treat the code as secondary.
On banking, the operator supports cards, e-wallets and cryptocurrency with a low minimum deposit. E-wallets are typically the fastest to pay out and bank transfers the slowest, with processing times of several days normal at the slow end. Withdrawals generally route back to the deposit method, so the wallet or card you tap at registration is likely the one you will be paid into. Marathonbet has been trading since 1997 and operates internationally through Curaçao licensing, having also held or operated under European authorisations including Alderney and the Spanish regulator, with the specific licence depending on the market you register in. Confirm the current terms on the official site at opt-in, since they vary by market and are revised regularly.
Gambling involves risk and is intended for adults aged 18 or over (or the legal age in your jurisdiction). Bonuses carry wagering requirements — read them in full before opting in, never stake more than you can afford to lose, and seek support if gambling stops being entertainment.
Promotional terms, eligibility and values are set by the provider and can change at any time. Always confirm the current terms on the official site before signing up or completing a purchase.