Marathonbet Promo Code WELCOME100 carries a 500% deposit bonus and 300 free spins on the casino side of the account, and most people now type that code with their thumbs rather than a keyboard. That changes the practical problem. The offer itself is fixed, but a small screen hides fields, autocorrect edits text you did not ask it to edit, and app-switching between a banking app and a betting app is where half-finished registrations go to die. This article is about the mechanics of getting the code attached on a phone, not about re-listing the bonus terms.
App or mobile browser: which to register in
There is no version of the code that works in one place and not the other. WELCOME100 is a registration-time promo code, and the field it belongs in is part of the signup form, wherever that form is rendered. What differs is the surrounding experience.
A mobile browser gives you the full-fat version of the signup page. You can zoom, you can scroll back up to re-read a term, you can open a second tab to check the terms page without abandoning the form, and you can paste the code from your clipboard without fighting a native text field. For a one-time task with a code in it, the browser is usually the lower-risk route.
An app is better afterwards. If you plan to use the sportsbook regularly — and the pricing is the genuine reason to, with margins publicised at around 1.5% on football and tennis and roughly 2.3% across the book — then in-play betting, cash out and bet editing are all easier with a persistent login and a native interface. A sensible split is to register in the browser where you can see the whole form, then install the app and log in once the account exists and the offer has attached.
Where the promo code field actually lives on a small screen
On desktop, a promo code box tends to sit visibly alongside the other registration fields. On mobile, forms are usually stacked and split into steps, and optional fields are the first thing a designer collapses to keep the screen short. That is why people miss it.
Places worth checking before you tap the final confirm button:
The last step of registration, below the personal details and above the terms checkboxes, where optional extras are normally grouped.
A collapsed row labelled as optional, a bonus code, or a referral field — often a single line with a small chevron that has to be tapped to expand.
A separate offer-selection screen, where you pick which welcome package you want rather than typing anything.
The deposit screen, if the form did not present a code box at all — some flows move the field there.
Account settings or a bonuses area, which is where you would look if the field genuinely did not appear during signup.
If you cannot find a field anywhere, do not deposit and hope. Stop and ask support in writing before funding the account, because the choice of welcome offer is generally not reversible afterwards.
Mobile-only quirks that break code entry
Almost every failed promo code on a phone comes down to something the phone did rather than something the user typed.
Autocapitalise and autocorrect. WELCOME100 is a word-shaped string with digits on the end, which is exactly the sort of thing a predictive keyboard likes to alter. Type it, then read it back character by character before moving on.
Trailing spaces. Keyboards insert a space after an autocomplete suggestion. A code with a space on the end can be rejected as invalid.
Clipboard formatting. Copying from a page can bring invisible characters with it. If a pasted code fails, delete it and type it manually.
Keyboard covering the field. On short screens the keyboard can hide the box you are filling and the error message underneath it. Dismiss the keyboard and scroll before you assume the entry was accepted.
Rotation resets. Turning the phone can re-render a multi-step form and, on some flows, clear fields you already filled. Keep the device in one orientation for the whole signup.
Double submission. On a weak connection, tapping confirm twice because nothing appeared to happen is a common way to end up with a confusing part-registration. Wait for the response.
Autofill mismatches. Saved addresses and names can be filled with old or abbreviated details, which matters later because identity verification has to match what you entered.
Choosing the right offer before you tap anything
The casino package attached to the code is staged across five deposits and comes with 300 free spins. The sportsbook runs its own separate offer, historically 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 have to choose between them, and you normally cannot switch later.
That decision is harder on a phone because the comparison is not on one screen. Before you start the form, read both sets of terms in a browser, where you can keep them open side by side or at least flip between tabs. Rollover on the casino package is reported at 35x on bonus credit plus a separate 30x on free-spin winnings, and 35x means the bonus amount has to be turned over thirty-five times before it behaves like ordinary money — worth working out against the deposit you actually intend to make rather than the headline. The full 500% is only reachable with €5,000 in deposits across the staged structure, which is not a realistic target for most people and should not drive the decision.
Declining both offers is a legitimate third option. It keeps your balance unencumbered and withdrawable, and for a sports-led account where the low margins are the real draw, it is often the cleaner answer.
Step by step on a phone
Open the official Marathonbet site for your country in your mobile browser and begin registration.
Fill the personal details exactly as they appear on the ID document you will later upload.
Set your currency deliberately — it usually cannot be changed afterwards.
Expand any collapsed optional section and enter WELCOME100 in the promo code field, then re-read it.
Select the sports or casino welcome offer on purpose, knowing you generally cannot switch.
Submit, then complete identity verification straight away using your phone camera rather than waiting until a withdrawal is pending.
Deposit at least the stated minimum and confirm on screen that the offer and its terms have attached before you place a bet or a spin.
Install the app afterwards if you want it, and log in to the account you have already created.
Depositing and verifying from a handset
Payment coverage is wide — cards, e-wallets and cryptocurrency — with a low minimum deposit, and all of those are usable from a phone. The mobile-specific risk is app-switching. Confirming an e-wallet or banking payment often bounces you out to another app and then back again, and if the return leg fails you can be left unsure whether the deposit landed. Wait for the balance to update in the account itself before retrying, rather than pushing a second payment through.
Verification is one thing phones do better than laptops. Photographing an ID and a proof of address with the device you are already holding is faster than scanning, provided the whole document is in frame, flat, and legible without glare. Getting this done at registration removes the most common cause of payout delay, because withdrawals cannot be processed until verification is complete and they generally route back to the deposit method. Withdrawal speed varies substantially by method regardless of device — e-wallets are typically fastest, bank transfers slowest, with several days normal at the slow end.
Keeping a record you can actually find later
Screenshot the confirmation that the code was accepted, the offer you selected, and the terms page as it appeared when you opted in. This takes ten seconds on a phone and is the single most useful thing you can do if a question about the bonus comes up weeks later. Terms vary by market and are revised regularly, so a dated screenshot of what you agreed to is worth more than a memory of it.
Also check which licensing entity covers your market during signup rather than afterwards. Marathonbet has been trading since 1997 and operates internationally under Curaçao licensing, having held or operated under additional European authorisations including Alderney and the Spanish regulator, with the applicable licence depending on where you register. That detail is usually in small print in a page footer, which on mobile means scrolling to the very bottom — easy to skip, and the wrong thing to skip.
The short version
Register in a mobile browser where the whole form is visible, hunt out the collapsed optional field, type WELCOME100 by hand and read it back, choose your welcome offer knowing the choice sticks, verify your identity immediately with the phone camera, and only then install the app for day-to-day use. The 500% and 300 free spins are what the code delivers; the small screen is simply where most of the avoidable mistakes happen.
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.